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English annotation-error seeds (en/seeds/errors)

A seed is a short markdown note from which a rule or a piece of knowledge grows. Each seed in this folder describes one typical error in English Universal Dependencies (UD) annotation. The error can sit in the text (learner or native-speaker mistakes such as a answer, has went, between you and I) or in the analysis (a wrong head, label, tag or feature, often made by parsers or LLM annotators). This page gives a summary of each one.

Every seed has the same sections: Gist, Conditions and exceptions, Examples and Sources. Many also have an "In UD" note that says how the phenomenon looks in a tree. Most seeds end with one or more ```rule blocks. The expert system (en/src/expert.rs) compiles these blocks and checks CoNLL-U trees against them. The target annotation style is UD English EWT 2.18.

Rule blocks

rule: en.errors.cop-be
what: cop not on be — become/seem/get are VERB with xcomp
match: c[rel=cop]
require: c[lemma=be]
severity: error
source: UD _en/dep/cop.md

Some seeds have no rule of their own. They point to a rule in another seed folder (for example en/seeds/nominal), or they are background notes that explain the method.

a-an-choice

a or an — by the first sound of the next word

Gist. The indefinite article is an before a vowel sound and a before a consonant sound. This includes vowel letters that are pronounced [j] or [w] (a unit, a eulogy, a one). What counts is the sound of the word right after the article, which is not always the noun. Errors like a answer come from typos and from learners.

Conditions and exceptions. The engine sees only spelling, so the rule fires only when nothing stands between the article and the noun. Known false alarms: a European, a one-off, an FBI agent. Abbreviations starting with M, N, R, S, X and silent h (an hour, an honest) are left out.

Examples. ✗ a answer, ✗ a order, ✗ a Immigrant; ✓ an apple, ✓ a big apple.

Machine-readable part. en.errors.a-before-vowel (warn): a directly before a noun that starts with a vowel letter. en.errors.an-before-consonant (warn): an directly before a noun that starts with a consonant letter.

Sources. Fowler, Modern English Usage (1926), "A, AN" §1; ERRANT (P17-1074, DET); BEA-2019 (W19-4406).

adjectives-in-names

An adjective in a name — amod, not compound

Gist. Since UD 2.8, adjectives and verbs inside proper names keep their own part of speech (ADJ, VERB), although the XPOS stays NNP. An adjective that modifies a noun is amod, not compound: United States → amod(States, United). The compound analysis is left over from automatic PTB conversion.

Conditions and exceptions. EWT keeps a few lexicalised pairs as compound: top notch, green tea, quarter end. Since UD 2.8, the lemma of an adjective inside a name is capitalised.

Examples. the United States → amod(States, United); Central Iowa → amod(Iowa, Central); Islamist officers → amod(officers, Islamist).

Machine-readable part. en.errors.adj-not-compound (warn): an ADJ attached to a noun as compound should be amod.

Sources. Zeldes & Schneider (2023.udw-1.7); UD guidelines en/dep/flat.

advcl-on-noun

advcl under a noun — should be acl

Gist. A clause that modifies a noun is acl (or acl:relcl). advcl modifies a predicate: a verb, an adjective, or a nominal predicate with a copula. An advcl under a noun that has no copula usually means the clause was attached to the nearest noun instead of the verb, or was given the wrong label.

Conditions and exceptions. A nominal predicate with a copula may take advcl (It was a mess when we arrived). In verbless fragments such as headlines and captions, the noun can be the root and take advcl.

Examples. a decision to leave → acl(decision, leave); I called when I arrived → advcl(called, arrived); It was a mess when we arrived → advcl(mess, arrived), because cop(mess, was) is present.

Machine-readable part. en.errors.advcl-on-noun (warn): advcl under a NOUN or PROPN that has no cop dependent.

Sources. UD guidelines en/dep/advcl, en/dep/acl; Bernhard et al. (2025.law-1.14, LLMs prefer shorter arcs); 2023.udw-1.7.

adverb-placement

An adverb between the verb and the object: "I like very much football"

Gist. In English, an adverb normally does not go between the verb and its direct object: ✓ I like football very much, ✗ I like very much football. Learners whose language has freer word order carry this habit over. ERRANT classes it as WO (word order).

Conditions and exceptions. A long ("heavy") object may move to the end of the clause: I understand better the risks that we face. Frequency adverbs (always, often, never) go before the verb, so after the verb they are already a word-order error.

Examples. ✗ I like very much football. ✓ I understand better the risks we face. (heavy object)

Machine-readable part. en.errors.adverb-before-object (warn): an advmod from a fixed list (much, well, often, always, never, usually, also, very) stands after the verb and before a nominal obj.

Sources. ERRANT (P17-1074, WO); Bryant et al. 2019 (W19-4406).

attraction-of-phrase

Attraction through an of-phrase: "A pattern of arrests indicate"

Gist. This is agreement attraction. The subject is a singular noun with a plural of-phrase, and the verb agrees with the nearer plural noun instead (A pattern of arrests indicate…). Fowler calls these nouns "red herrings". Quantity nouns are the exception: with a lot of, a number of, the majority of, half of and similar, the of-phrase decides the number.

Conditions and exceptions. The list of quantity and collective nouns is open (lot, number, majority, rest, half, percent, bunch, couple, variety, group, kind, sort, type, …), and the rule skips these lemmas. The rule cannot tell a coordinated subject, which is legitimately plural, from attraction.

Examples. ✗ A pattern of arrests and seizures indicate…; ✗ The return to flight activities are funded.; ✓ A number of people believe…

Machine-readable part. en.errors.attraction-of (warn): a singular NOUN subject with a plural nmod, and the verb is VBP. en.errors.attraction-of-auxcop (warn): the same pattern with a VBP copula or auxiliary. Both rules exempt quantity and collective lemmas.

Sources. Fowler 1926, NUMBER §4 "Red herrings"; Zacharopoulos et al. (2023.emnlp-main.998); BLiMP (2020.tacl-1.25); Garcia et al. (2025.depling-1.4).

clausal-subject-csubj

A clausal subject — csubj, not nsubj

Gist. When the subject is a whole clause (That he lied is obvious, Taking a nap will relax you), the relation is csubj, and it attaches to the verb of that clause. nsubj on a word tagged VERB is almost always wrong. LLMs learn csubj late and use it inconsistently.

Conditions and exceptions. A verbal noun (The swimming was fun, NN) is nsubj. EWT tags following in the following is… as VERB with nsubj. For it-extraposition, see tough-vs-extraposition.

Examples. Whether he lied is beside the point → csubj(point, lied); Taking a nap will relax you! → csubj(relax, Taking).

Machine-readable part. en.errors.verb-subject-csubj (warn): nsubj or nsubj:pass on a VERB.

Sources. UD guidelines en/dep/csubj; Matsuda et al. (2026.udw-1.1); Dönicke et al. (2020.udw-1.8).

consistency-detection-methods

How to find annotation errors automatically

Gist. This background seed has no rule of its own. Errors in a treebank or in parser output leave statistical traces, and several independent methods can find them. Each method suggests a different kind of rule:

  1. Variation nuclei. The same word pair in the same context gets different relations in different sentences.
  2. Arc direction. Compare the share of right-pointing dependents per relation across treebanks of one language. This seed is where the direction rules come from: flat and conj point right, compound and nummod point left, and cc comes before its conjunct.
  3. UPOS-trigram divergence. A symmetric KL measure between treebanks.
  4. Cross-parsing. Train on one treebank, test on another, and read the confusion matrix.
  5. Robustness to small edits. For example, swap a year in a sentence. Places where the parse changes are candidates for errors.

Conditions and exceptions. A rule that fires often on the gold standard is either wrong or is catching errors in the gold standard itself. Real gold errors found this way include Case=Nom on it after a preposition, det on soldiers in an old soldiers' home, and Number=Plur on species.

Examples. The English compound and csubj relations are among the least consistent across treebanks. The obl/nmod pair is the top parser confusion in EWT and GUM.

Sources. de Marneffe et al. 2017 (W17-6514); Dickinson 2009; Dönicke et al. (2020.udw-1.8); Aggarwal & Zeman (2020.tlt-1.9); Zeldes & Schneider (2023.udw-1.7); Kalpakchi & Boye (2021.udw-1.8).

coordinated-subject-agreement

Subject "X and Y" — the verb is plural

Gist. A subject made of two or more parts joined by and is plural: Mother and children were killed. Agreeing with the nearest conjunct is an error. With or/nor, the verb agrees with the nearest alternative instead.

Conditions and exceptions. These take the singular:

A verb placed before the subject may be singular (There is a table and some chairs), so the rule only checks subjects that come before the verb.

Examples. ✗ green curry and red curry is awesome → ✓ are; ✗ Mercury and Venus is conjunct; ✓ Mother or children are to die.

Machine-readable part. en.errors.coord-subject-verb (warn): a subject with conj + cc and before the verb, and the verb is VBZ. en.errors.coord-subject-auxcop (warn): the same with a VBZ copula or auxiliary. Neither fires if a conjunct follows the verb or the subject has each/every.

Sources. Fowler 1926, NUMBER §2–3, 7, and IS §4; ERRANT (P17-1074, VERB:SVA); BLiMP (2020.tacl-1.25).

coordination-structure

Coordination: the head is the first conjunct, cc is on the next one

Gist. In UD v2, the first conjunct heads a coordination "X, Y and Z". Y and Z attach to X as conj, and the conjunction attaches as cc to the conjunct that follows it. So conj always points left to right, and cc comes before its head. SD and UD v1 attached cc to the first conjunct, and old converters and models still do this.

Conditions and exceptions. A sentence-initial conjunction (But he left) is cc of the root and still comes before its head. Paired conjunctions either/both/neither are cc:preconj.

Examples. apples and pears → conj(apples, pears), cc(pears, and); He came, saw and conquered → conj(came, saw), conj(came, conquered), cc(conquered, and).

Machine-readable part. en.errors.conj-rightward (error): conj must follow its head. en.errors.cc-before-conjunct (warn): cc must precede its head.

Sources. UD guidelines en/dep/conj, en/dep/cc; Peng & Zeldes (W18-4918); Przepiórkowski & Woźniak (2023.acl-long.864); Grünewald et al. (2021.eacl-main.67); Maier et al. 2012 (coordination in the PTB).

copula-be-only

The copula is only be; seem, become, get — xcomp

Gist. In English UD, cop is only predicative be, and the nominal or adjectival predicate is the head (Bill is honest → cop(honest, is)). Verbs like become, seem, get, remain, look are ordinary VERBs with xcomp. With a verbal predicate, be is aux or aux:pass. The one exception is a clausal predicate with nsubj:outer (The problem is that…): there be is cop of the clause's verb.

Conditions and exceptions. Existential there is has be as a VERB root (see existential-there). Hyphenated former participles (mouth watering, self-cleaning) sometimes show VERB + cop in EWT. Treebanks without lemmas (ESLSpok) give false alarms for the first rule.

Examples. Bill got rich → xcomp(got, rich); Bill is speaking → aux(speaking, is); The important thing is to keep calm → nsubj:outer(keep, thing), cop(keep, is).

Machine-readable part. en.errors.cop-be (error): cop whose lemma is not be. en.errors.cop-on-verb (warn): cop under a VERB with no nsubj:outer or csubj:outer.

Sources. UD guidelines en/dep/cop; Bernhard et al. (2025.law-1.14, perfect confused with copula).

dep-last-resort

dep — only as a last resort

Gist. dep means "a relation exists, but it could not be determined". It is for odd constructions and for failures of a converter or parser. The hand-checked EWT gold standard has almost none, so an annotator that uses dep often is giving up on the analysis. LLMs do this on repetitions, ellipsis and abbreviations.

Conditions and exceptions. GUM uses dep much more widely, for spoken fragments and, in older releases, for number identifiers (Page 3). In EWT style, every dep is a reason to recheck the parse. Ellipsis has its own mechanisms: orphan and promotion (see gapping-orphan).

Examples. Then, as if to show that he could, … → dep(show, if) (the guideline example).

Machine-readable part. en.errors.dep-last-resort (warn): every dep relation is flagged.

Sources. UD guidelines en/dep/dep; 2023.udw-1.7; Kellert et al. (2025.findings-emnlp.863).

determiner-noun-number

Determiner and noun — same number

Gist. this/that and a/an go with singular nouns, and these/those go with plurals. A mismatch is either an error in the text or a wrong Number feature on the noun. Learner corpora class these errors as DET and NOUN:NUM.

Conditions and exceptions.

Examples. ✗ this times; ✗ these question; ✗ a monthly breakfasts; ✗ an SAP identification numbers; ✓ a few weeks.

Machine-readable part. en.errors.a-singular (warn): a as det of a plural noun, unless a quantity word (few, good, full, estimated, further, extra, additional, mere, whopping, great, total) is attached to the noun. The demonstrative check is rule en.nominal.dem-number in A demonstrative agrees with its noun in number.

Sources. BLiMP (2020.tacl-1.25, determiner–noun agreement); ERRANT (P17-1074); W19-4406; Fowler 1926, A, AN §2; Poutsma, A Grammar of Late Modern English III ch. XXVI, IV ch. XL.

double-comparative

Double comparison: more happier

Gist. English forms the comparative either with a suffix (happier) or with more/most (more beautiful), never with both: ✗ more happier, ✗ most easiest. ERRANT classes this as ADJ:FORM.

Conditions and exceptions. more as a quantity (more people) is out of scope. Only advmod on a JJR/RBR counts. Archaic most unkindest is a stylistic exception.

Examples. ✗ The customers are more happier. → ✓ happier; ✓ more beautiful.

Machine-readable part. No rule here. The check is rule en.nominal.double-comparison in more/most + adjective: the adjective itself is in the positive degree. In UD the pattern is advmod(happier, more) with happier as JJR.

Sources. ERRANT (P17-1074, ADJ:FORM); W19-4406.

double-negation

Double negation: don't know nothing

Gist. Standard English has one negation per clause: I don't know anything or I know nothing. not/n't together with a negative pronoun or determiner in the same clause is negative concord (I don't know nothing). It is normal in many dialects and in Slavic languages, but an error in the standard.

Conditions and exceptions. Deliberate double negation that makes a positive (not unhappy, I can't not go) is fine. So is dialect speech quoted on purpose.

Examples. ✗ I don't think nothing of it. → ✓ anything; ✗ didn't take no reason.

Machine-readable part. en.errors.double-negation-pronoun (warn): a Polarity=Neg advmod and a PronType=Neg dependent on the same predicate. en.errors.double-negation-det (warn): a Polarity=Neg advmod, plus a PronType=Neg det inside an obj/obl/nsubj of the same predicate.

Sources. Findlay et al. (2025.udw-1.8); BLiMP (2020.tacl-1.25, NPI licensing).

english-treebank-conventions

Convention differences between the English UD treebanks

Gist. The 13 English UD treebanks (UD 2.18) differ in two ways: some lack certain columns, and some annotate the same thing differently. A rule built on EWT can give false alarms elsewhere. The expert system checks EWT 2.18 style, so on other treebanks compare violations with this list first.

Conditions and exceptions.

phenomenonEWTGUM
Sri Lanka, Hong Kongcompound, head on the rightflat, head on the left
Page 3 (before 2.11)nummoddep
Marvel Consultants, Inc.head Inc.head Consultants (nmod:desc since 2.15)
ADJ in namesoften compoundamod
PP on a fragment root (Good morning to all)nmodobl
deprarefrequent
iobj outside double-object verbsalmost neversometimes (presented me)
orphan outside a conjunctneversometimes

Alignment across versions: 2.7–2.8 added MWTs for clitics, hyphens as separate tokens, and ADJ/VERB in names. 2.10 moved proper names from flat to transparent syntax. 2.11 added nsubj:outer and revised relative clauses, clefts and possessive lemmas. 2.15 introduced :unmarked and nmod:desc.

Examples. If a rule fires much more often on GUM than on EWT, that points to a convention difference, not a faulty rule.

Sources. Zeldes & Schneider (2023.udw-1.7); Schneider & Zeldes (2021.udw-1.14); Dönicke et al. (2020.udw-1.8).

errant-taxonomy

The ERRANT error taxonomy and what of it is visible in UD

Gist. This background seed has no rule of its own. ERRANT classifies each text edit deterministically from part-of-speech tags, lemmas and a dictionary. It has 25 main types (ADJ, ADJ:FORM, ADV, CONJ, CONTR, DET, MORPH, NOUN, NOUN:INFL, NOUN:NUM, NOUN:POSS, ORTH, OTHER, PART, PREP, PRON, PUNCT, SPELL, UNK, VERB, VERB:FORM, VERB:INFL, VERB:SVA, VERB:TENSE, WO). Each type combines with an operation: M (missing), R (replaced) or U (unnecessary).

For verbs, ERRANT applies ordered tests: same in lower case → ORTH; not a word → SPELL; same lemma → look at the form; one side VBG/VBN → FORM; VBD → TENSE; VBZ → SVA.

Conditions and exceptions. The types that leave a trace in a UD tree each have their own seed here:

UD keeps text errors in the tree (see literal-annotation-learner). So the agreement and form rules in this folder also work as grammatical-error detectors.

Examples. Verb rules from the paper: [iss → is] SPELL; [IS → is] ORTH; [has → is] VERB; [being → is] VERB:FORM; [was → is] VERB:TENSE; [are → is] VERB:SVA.

Sources. Bryant et al. 2017 (P17-1074); Bryant et al. 2019 (W19-4406); Choshen et al. (2020.conll-1.7, SERCL); Koyama et al. (2025.acl-long.1026, CTSEG).

existential-there

Existential there: expl, and be is a VERB

Gist. In There is a ghost in the room, there is a dummy subject: PRON, XPOS EX, relation expl. The real subject is ghost (nsubj), and is is the root with UPOS VERB, not AUX and not cop. The verb agrees with the subject that follows it (There are two dogs).

Conditions and exceptions. Locative there (I went there) is ADV with advmod. Colloquial there's + plural is common, so the rule only warns. Fowler allows the singular before a coordinated subject.

Examples. There's a cow in the field → expl('s, There), nsubj('s, cow), 's: VERB; ✗ Is there any tricks I could use? → ✓ Are there.

Machine-readable part. en.errors.there-be-verb (warn): the head of expletive there must be VERB. en.errors.there-agreement (warn): VBZ with expletive there and a plural nsubj. The rule en.nominal.ex-there lives in Existential there is a subject pronoun without locative meaning.

Sources. UD guidelines en/dep/expl, en/dep/cop; Fowler 1926, NUMBER §2, 7; ERRANT (P17-1074, VERB:SVA).

flat-compound-direction

flat — head on the left, compound — head on the right

Gist. An English compound noun has its head on the right (phone book → compound(book, phone)), so compound dependents come before the head. flat is for headless names (Hillary Rodham Clinton): every part attaches to the first word, so flat dependents always come after it. A compound after its head, or a flat before its head, means a wrong head or a flipped analysis.

Conditions and exceptions. compound:prt (made up) follows the verb. Participles with particles (rusted out) have compound after the head in EWT. A place name with the generic word first is flat (Lake Mead, Mount Everest). With the generic word last it is compound (Mirror Lake). Treebanks differ: for Sri Lanka, EWT has compound and GUM has flat.

Examples. oil price futures → compound(price, oil), compound(futures, price); Carl XVI Gustaf → flat(Carl, XVI), flat(Carl, Gustaf).

Machine-readable part. No rule here. The checks are rules en.nominal.flat-head-first (Personal names and "type + name" — flat, head first) and en.nominal.compound-head-final (A noun modifier before the head noun: compound).

Sources. UD guidelines en/dep/compound, en/dep/nmod-desc, en/dep/flat; 2023.udw-1.7; Schneider & Zeldes (2021.udw-1.14); Dönicke et al. (2020.udw-1.8).

function-words-leaves

Function words are leaves of the tree

Gist. In UD, content words are heads. Function words (aux, cop, case, mark, cc, det, punct) attach to them and have almost no dependents of their own. Only fixed, goeswith, conj between function words (before and after) and a modifying advmod (just before) are allowed. An auxiliary with a subject or object means the tree is upside down, in the PTB/SD style where the function word is the head.

Conditions and exceptions. In VP ellipsis (Mary will too), will is the head of the clause, not aux (see vp-ellipsis-aux-head). Coordinated function words linked by conj are allowed.

Examples. He has eaten → aux(eaten, has), nsubj(eaten, He), not nsubj(has, He); in the house → case(house, in), det(house, the).

Machine-readable part. en.errors.aux-cop-leaf (error): aux/aux:pass/cop with a core or content dependent. en.errors.function-word-leaf (warn): cc/mark/case/det with a content dependent. en.errors.punct-leaf (error): punct with dependents.

Sources. UD guidelines en/dep/aux_, en/dep/cop, en/dep/punct; W15-2134; 2025.law-1.14.

gapping-orphan

Gapping: orphan links the remnants of an omitted predicate

Gist. In Marie went to Paris and Miriam to Prague, the second verb is missing (gapping). UD promotes one remnant (Miriam) to the verb's place, conj(went, Miriam), and attaches the other remnants to it with orphan: orphan(Miriam, Prague). So the head of an orphan is always the promoted remnant: a conjunct, or in fragments a root, advcl or parataxis.

Conditions and exceptions. orphan is not used when verbal material remains, as in right-node raising or VP ellipsis. GUM identifies ellipsis more broadly and uses orphan in more contexts. In learner text, the choice between ellipsis and asyndetic coordination depends on whether the sentence is judged grammatical.

Examples. Marie went to Paris and Miriam to Prague → orphan(Miriam, Prague); John bought and ate an apple → conj(bought, ate), obj(bought, apple), with no orphan.

Machine-readable part. en.errors.orphan-head (warn): the head of orphan must be conj/root/advcl/parataxis.

Sources. UD guidelines en/dep/orphan; Corbetta et al. (2025.tlt-1.6); 2023.udw-1.7; W18-4918; Dickinson & Ragheb 2015 (grammaticality in learner annotation).

iobj-bare-nominal

iobj — a bare noun before obj; "to X" — obl

Gist. An English indirect object is only a bare nominal in a double-object construction: She gave me a raise → iobj(gave, me), obj(gave, raise). A recipient with to/for (gave it to me) is obl, because prepositional phrases are not core arguments in English. The indirect object stands between the verb and the direct object.

Conditions and exceptions. The direct object can come earlier when it is fronted (How much money does the USA give NASA?), so the order check only looks at an obj after the verb. Relative and interrogative pronoun objects (the book that I gave him) are out of scope.

Examples. ✓ give the children the toys → iobj(give, children), obj(give, toys); ✓ give the toys to the children → obl(give, children), case(children, to); ✗ iobj(give, children) together with case(children, to).

Machine-readable part. en.errors.iobj-no-case (error): iobj with a case dependent. en.errors.iobj-before-obj (warn): iobj after a nominal obj that follows the verb.

Sources. UD guidelines en/dep/iobj, en/dep/obl; Matsuda et al. (2026.udw-1.1).

iobj-verb-classes

iobj — only with double-object verbs

Gist. Only a limited class of verbs takes two bare objects:

explain, describe, suggest, say, announce, mention, propose, introduce, donate do not: ✗ explain me the rule → ✓ explain the rule to me. LLMs make the opposite mistake and put iobj on the only object of help, let, call.

Conditions and exceptions. The class is open: rare verbs like envy, forgive, spare, fine, bill also take two objects. EWT uses iobj with tell, ask, trust, notify even without a direct object (tell me about it), so the check looks at the verb, not at whether an obj is present. GUM uses iobj more widely.

Examples. ✓ She told me the news. ✗ Can you explain me this? ✓ Help me! → obj(Help, me).

Machine-readable part. en.errors.no-double-object (warn): iobj under explain, describe, suggest, say, announce, mention, propose, introduce, donate, repeat, dedicate, confess. The licensing list is rule en.lexicon.iobj-verb in Verbs that take an indirect object.

Sources. UD guidelines en/dep/iobj; ERRANT (P17-1074, VERB, PREP); 2026.udw-1.1.

literal-annotation-learner

Text with errors is annotated literally

Gist. UD describes what is written, not what was meant: an ungrammatical sentence gets the tree of its actual words ("literal reading", as in the TLE learner treebank). Spelling errors have their own mechanism:

Grammatical errors (agreement, verb form) do not get Typo. An LLM annotator tends to correct silently, tagging what was meant. The agreement rules then stay silent and the text error is lost.

Conditions and exceptions. Deliberate non-standard forms (should of, ain't, them boys) are Style, not Typo (see vernacular-style). A missing word is analysed as ellipsis. Extra words in speech are reparandum. Whether a sentence counts as grammatical affects the choice between ellipsis, coordination and listing, so this principle should be stated explicitly.

Examples. He new it → new: lemma know, VBD, Typo=Yes, CorrectForm=knew; My wife know my secret → know: VBP, no Typo.

Sources. Berzak et al. (P16-1070, TLE); Masciolini et al. (2025.udw-1.17); Dickinson & Ragheb 2015; Kyle et al. (2022.bea-1.7, SL2E).

llm-annotator-failure-modes

Typical failures of LLM annotators for UD

Gist. This background seed has no rule of its own. It lists the recurring ways LLMs fail at UD annotation, each with a matching check in this folder:

  1. Tags are better than trees, so check heads and relations first.
  2. Arcs are too short: the model prefers the nearest head (see obl-on-nominal, advcl-on-noun, vp-ellipsis-aux-head).
  3. Labels outside the tag set, including det:poss and old SD/UD v1 labels (neg, dobj, nsubjpass, cc on the first conjunct).
  4. Rare relations (iobj, csubj) are unstable.
  5. Inconsistency on repetitions, ellipsis and abbreviations.
  6. Self-generated rules are too narrow and ignore word order.
  7. Formal defects: invalid CoNLL-U, occasional cycles.
  8. Accuracy drops as the number of clauses grows.
  9. Silent correction of the text (see literal-annotation-learner).

Conditions and exceptions. Accuracy must be measured against an independent gold standard, not against corrected LLM output. These help: a step-by-step order (UPOS → head → relation), tabular output, examples chosen by similarity, and using the LLM as an editor of an existing parse. Mova's "draft" mode works this way: the deterministic Rust annotator parses first, and an LLM corrects.

Examples. Typical LLM outputs: det:poss instead of nmod:poss; a prepositional phrase attached to the nearest noun instead of the verb.

Sources. Bernhard et al. (2025.law-1.14); Machado & Ruiz (2024.propor-1.46); Kellert et al. (2025.findings-emnlp.863); Matsuda et al. (2026.udw-1.1, 2025.iwpt-1.2); Ginn & Palmer (2025.xllm-1.17); 2026.lrec-1.910.

missing-article

A missing article with a countable noun

Gist. A singular count noun cannot stand bare. It needs an article, possessive, numeral or other determiner (I have a car, not I have car). The superlative also needs the. Dropped articles are among the most frequent errors of speakers whose language has no articles.

Conditions and exceptions. Telegraphic style in reviews and headlines (Room was amazing), fixed phrases (go to school, by car, in bed), and mass readings (give him room to progress) are fine. The rule covers only a few dozen clearly countable nouns used as subject or object.

Examples. ✗ Now I have wife and son.; ✗ I have friend who drive from…; ✗ and did great job.

Machine-readable part. en.errors.bare-count-noun (warn): an NN obj/nsubj/nsubj:pass from a fixed list of count nouns (car, book, friend, job, wife, …) with no det, nmod:poss, nummod or det:predet. It does not fire when the noun is sentence-initial (an article dropped at the start).

Sources. W19-4406 (DET); ERRANT (P17-1074, M:DET); Berzak et al. (P16-1070); Jespersen, The Philosophy of Grammar (1924), on prosiopesis.

missing-copula

A missing copula: "He very happy"

Gist. English cannot drop be: He is very happy. Learners whose language has a zero present-tense copula write ✗ He very happy. Under literal annotation, such a sentence has a nominal or adjectival predicate with nsubj but no cop. The same tree also appears when an existing copula was attached to the wrong word.

Conditions and exceptions. Telegraphic reviews and headlines (Rooms clean.) are fine. Absolute constructions (with the kids asleep) are advcl and out of scope: the rule only checks root, conj, ccomp and parataxis.

Examples. ✗ Evidently, this a problem that… → nsubj(problem, this) with no cop; ✓ Rooms very clean (review style).

Machine-readable part. en.errors.missing-copula (warn): a NOUN/ADJ/PROPN predicate with a preceding nsubj and no cop/aux. It does not fire if the sentence has no finite verb at all (telegraphic style).

Sources. Berzak et al. (P16-1070); ERRANT (P17-1074, M:VERB); Dickinson & Ragheb 2015; UD guidelines en/dep/cop.

modal-do-to-base

After a modal, do and to — the base form

Gist. A modal (can, will, must, should), auxiliary do and the particle to require the base form (VB): can go, does not know, to see. If another auxiliary comes in between (could have gone, will be going, to be told), that auxiliary decides the form. Errors like can goes, to going, will meeting are ERRANT VERB:FORM.

Conditions and exceptions. In an auxiliary chain, the last auxiliary before the lexical verb decides its form. So if the verb is not VB, the rules require another auxiliary after the modal, do or to. Dialectal should of took is covered in vernacular-style.

Examples. ✗ We will meeting Rod's office.; ✗ it does has one; ✓ don't get married (get is aux:pass).

Machine-readable part. en.errors.to-base, en.errors.modal-base, en.errors.do-base (warn): a VERB tagged VBN/VBG/VBD/VBZ/VBP with to (mark), an MD aux or do aux, and no further auxiliary after it.

Sources. ERRANT (P17-1074, VERB:FORM); W19-4406; Koyama et al. (2025.acl-long.1026); UD guidelines en/dep/aux_, en/dep/mark.

much-many-countability

much, many and countability

Gist. many goes with plural count nouns (many books), and much goes with singular mass nouns (much time). Mass nouns have no plural: information, advice, furniture, equipment, knowledge, homework, luggage, evidence, feedback, software (✗ informations). These errors are typical of speakers whose language treats these nouns as countable.

Conditions and exceptions. Adverbial much (much bigger, not much) is out of scope; only amod/det on a noun counts. many a man is singular (literary). Nouns with established plurals in some senses (accommodations, damages, researches, staffs) are not on the mass list.

Examples. ✗ this has caused much difficulties; ✗ much monies; ✗ storage for your luggages.

Machine-readable part. en.errors.much-plural (warn): much on a plural noun. en.errors.many-singular (warn): many on a singular noun. The mass-noun plural check is rule en.nominal.mass-no-plural in Uncountable nouns: information, advice, furniture.

Sources. ERRANT (P17-1074, NOUN:INFL, NOUN:NUM); W19-4406.

negation-not

not and n't: PART, advmod, Polarity=Neg

Gist. The negative particle not/n't in English UD is PART with XPOS RB, relation advmod and feature Polarity=Neg. Negative pronouns and determiners (no, nothing, nobody, none) carry PronType=Neg. The SD/UD v1 label neg no longer exists. The features sit on the negative word, not on the predicate, so they record form, not meaning.

Conditions and exceptions. not can have other relations: cc with ExtPos=CCONJ in not only … but, conj in whether or not, and fixed. So the rule checks only UPOS, XPOS and the feature. Treebanks without features (ESLSpok) fail it by convention.

Examples. He did n't go → advmod(go, n't); n't: PART, RB, Polarity=Neg. no problem → det(problem, no); no: DET, PronType=Neg.

Machine-readable part. en.errors.not-part (error): every not/n't must be PART, RB, Polarity=Neg.

Sources. Findlay et al. (2025.udw-1.8); UD guidelines en/feat/Polarity.

nmod-on-predicate

nmod under a verb or adjective — should be obl

Gist. This is the mirror image of obl-on-nominal: nmod is only for dependents of nouns. A prepositional phrase on a verb is always obl, and on an adjective too (afraid of sharks). nmod under a verb is left over from UD v1, which used one nmod for all prepositional phrases.

Conditions and exceptions. Quantity adjectives used as pronouns take nmod: most of them, many of the people, much of the time, few of us.

Examples. people afraid of sharks → obl(afraid, sharks); He talked about it → obl(talked, it); most of them → nmod(most, them).

Machine-readable part. en.errors.nmod-on-verb (error): nmod under a VERB. en.errors.nmod-on-adj (warn): nmod under an ADJ other than most, many, much, few, more, little, less, least, several, enough.

Sources. UD guidelines en/dep/obl, en/dep/nmod, English migration guidelines; 2023.udw-1.7.

nominal-rels-on-verb

Nominal relations do not come off a verb

Gist. Some relations belong to the noun phrase by definition: amod (adjective on a noun), acl (clause on a noun) and case (preposition in a nominal). If their head is a verb, either the relation or the head's part of speech is wrong:

Conditions and exceptions. EWT tags following in the following as VERB with det. A work title that is a clause ("What We've Lost", published by…) gives acl from a VERB.

Examples. by using it → mark(using, by); the man sitting there → acl(man, sitting); He left, crying → advcl(left, crying).

Machine-readable part. en.errors.acl-on-verb, en.errors.amod-on-verb, en.errors.case-on-verb (warn): the respective relation under a VERB.

Sources. UD guidelines en/dep/case, en/dep/mark, en/dep/acl, en/dep/amod; 2025.law-1.14.

numbered-entities-nummod

nummod — only quantity and only before the noun

Gist. nummod is a numeral that says "how many": 3 sheep, forty dollars. A number after a noun is an identifier, not a quantity (page 394, Route 66, World War II). Under the UD 2.18 guidelines it is flat from the generic word. So nummod after a noun is an error, and so is nummod on a non-numeral (several, many are amod or det).

Conditions and exceptions. Money: in $ 40, nummod($, 40) is correct. The rule only checks NOUN and PROPN heads. A phone number after number: is appos. Dates and addresses are nmod:unmarked.

Examples. Sam ate 3 sheep → nummod(sheep, 3); page 394 → flat(page, 394); door number 3 → flat(door, number), flat(number, 3).

Machine-readable part. No rule here. The checks are rules en.nominal.nummod-before-noun and en.nominal.nummod-num in Cardinal numeral on a noun: nummod on NUM, before the noun.

Sources. UD guidelines en/dep/nummod, en/dep/nmod-desc (Numbered Entities); 2023.udw-1.7; 2021.udw-1.14; Kalpakchi & Boye (2021.udw-1.8).

obj-without-preposition

The direct object and the subject have no preposition

Gist. obj is a direct object without a preposition. As soon as the phrase has a case preposition, it is obl on a verb or nmod on a noun, and the same holds for subjects. Prepositional verbs (depend on, look at, listen to, refer to) have a semantic "object", but syntactically it is obl.

Conditions and exceptions. Possessive 's is also case, but it attaches to the possessor (nmod:poss), so the rule only counts ADP. Inversion with a fronted prepositional phrase (Under the bed is a box) is obl + nsubj in EWT.

Examples. I depend on you → obl(depend, you), case(you, on); Refer to our brochure → obl(Refer, brochure); ✗ obj(depend, you) with case(you, on).

Machine-readable part. en.errors.obj-no-preposition (error): obj with an ADP case. en.errors.subject-no-preposition (warn): any nsubj* with an ADP case.

Sources. UD guidelines en/dep/obj, en/dep/obl, en/dep/nsubj.

obl-on-nominal

obl under a noun — suspected nmod

Gist. A prepositional phrase is labelled by what it attaches to: obl on a verb, adjective or adverb, and nmod on a noun. So obl under a noun means either the phrase really belongs to the verb (wrong head) or the label should be nmod. Confusing obl and nmod is the most common error of English parsers, and it is almost always a prepositional-phrase attachment error (eat a pizza with a fork vs with anchovies).

Conditions and exceptions.

Examples. a preference for lilies → nmod(preference, lilies); we prefer lilies to daisies → obl(prefer, daisies); eat a pizza with a fork → obl(eat, fork), but with anchovies → nmod(pizza, anchovies); He was a teacher in Boston → obl(teacher, Boston), because cop(teacher, was) is present.

Machine-readable part. en.errors.obl-on-nominal (warn): obl under a NOUN/PROPN/PRON that has no cop.

Sources. UD guidelines en/dep/obl, en/dep/nmod; Zeldes & Schneider (2023.udw-1.7); Peng & Zeldes (W18-4918); 2025.law-1.14.

one-subject-one-object

One subject and one direct object per predicate

Gist. A predicate has at most one subject (nsubj, nsubj:pass, csubj) and at most one direct object. Two subjects mean the roles are mixed up. A typical case is an object relative clause (the book that the students read): that is obj and students is nsubj, but an annotator makes both subjects. Another case is a subordinate-clause subject attached to the main verb.

Conditions and exceptions. The outer subject of a copular sentence with a clausal predicate is nsubj:outer and does not count (The problem is that this has never been tried). Coordinated subjects are one nsubj plus conj.

Examples. the book that the students read → obj(read, that), nsubj(read, students); The problem is that this has never been tried → nsubj:outer(tried, problem), nsubj:pass(tried, this).

Machine-readable part. en.errors.one-subject (error): a second subject on the same predicate. en.errors.one-object (error): a second obj on the same predicate.

Sources. UD guidelines en/dep/nsubj, en/dep/nsubj-outer, en/dep/obj, en/dep/cop; 2023.udw-1.7; BLiMP (2020.tacl-1.25).

overregularized-verbs

Regular endings on irregular verbs: goed, buyed

Gist. Learners and children regularise irregular verbs with -ed: goed, buyed, thinked, catched (ERRANT VERB:INFL). Under UD conventions and EWT practice, the wrong form stays as written. It gets Typo=Yes, the lemma and tag of the intended word (VBD/VBN), and CorrectForm in MISC.

Conditions and exceptions. Real words that look like such forms (seed, leaved, payed) are not on the list.

Examples. I buyed it → buyed: lemma buy, VBD, Typo=Yes, CorrectForm=bought; ✗ We goed home without Typo=Yes.

Machine-readable part. en.errors.overregularized-typo (warn): a form from a fixed list (goed, comed, buyed, thinked, …, weared) without Typo=Yes.

Sources. ERRANT (P17-1074, VERB:INFL); BLiMP (2020.tacl-1.25, irregular forms); Masciolini et al. (2025.udw-1.17).

passive-agent

Passive agent — obl:agent

Gist. In a passive clause, the by-phrase naming the agent is obl:agent. But by can also mark means or a time limit (transported by land, by the 1920s), and then it is plain obl. The meaning decides. A formal hint: an agent usually has an article or possessive (by the dog, by his wife), while means is a bare noun (by car, by hand).

Conditions and exceptions. Temporal by with an article (by the end of the year) is obl. Proper names and pronoun agents (by John, by them) are not checked, because they have no article.

Examples. The cat was chased by the dog → obl:agent(chased, dog); Arms are transported by land → obl(transported, land).

Machine-readable part. en.errors.by-agent (warn): in a passive (VBN with aux:pass), a plain obl with case by and a det/nmod:poss should probably be obl:agent.

Sources. UD guidelines en/dep/obl, en/dep/obl-agent.

passive-structure

Passive: nsubj:pass and aux:pass — only with a VBN participle

Gist. The English passive is be/get + past participle (VBN). So aux:pass and nsubj:pass occur only with a VBN head, and with aux:pass the subject must be nsubj:pass. Typical mistakes:

Conditions and exceptions. Reduced passives without an auxiliary are legitimate. Examples are headlines (Passport needed) and absolutes (many staffed by former officers): nsubj:pass on a VBN with no aux:pass.

Examples. The cat was chased by the dog → nsubj:pass(chased, cat), aux:pass(chased, was), obl:agent(chased, dog); The door opened → nsubj(opened, door); He got fired → aux:pass(fired, got).

Machine-readable part. en.errors.nsubjpass-vbn (error): nsubj:pass with a non-VBN head. en.errors.auxpass-vbn (error): aux:pass with a non-VBN head. en.errors.auxpass-subject (error): aux:pass together with a plain nsubj.

Sources. UD guidelines en/dep/nsubj-pass, en/dep/aux-pass, en/dep/cop; Bernhard et al. (2025.law-1.14); ERRANT (P17-1074, VERB:FORM).

perfect-have-vbn

Perfect: have + participle (VBN)

Gist. Perfect have requires a past participle: has gone, have seen. ✗ has went, ✗ have saw, ✗ has go confuse VBD and VBN, typically with irregular verbs (ERRANT VERB:FORM, VERB:INFL). If another auxiliary follows have (has been going), that auxiliary decides the form.

Conditions and exceptions. have to ("must") and lexical have are VERB, not aux. For regular verbs, VBD and VBN look the same (missed), so here the rule catches a tagging error, not a text error.

Examples. ✗ He has went home. ✓ He has been working.

Machine-readable part. en.errors.have-vbn (warn): a VERB tagged VB/VBD/VBZ/VBP/VBG with perfect have as aux and no further auxiliary after it.

Sources. ERRANT (P17-1074); BLiMP (2020.tacl-1.25, irregular forms); UD guidelines en/dep/aux_.

plural-subject-singular-verb

Plural subject with VBZ

Gist. A present-tense verb agrees with its subject in number: The results reduce, not reduces. A plural subject with a VBZ verb, copula or auxiliary has one of two causes:

Both people and models make more errors when the attractor stands right before the verb.

Conditions and exceptions. These are fine with VBZ:

Subjects after the verb (there's lots of…) are handled in existential-there.

Examples. ✗ The results of the test reduces the gas.; ✗ My parents even plays with them.; ✗ what people knows about Philippines.

Machine-readable part. en.errors.plural-subject-vbz (warn): a plural NOUN/PRON subject before a VBZ verb. en.errors.plural-subject-vbz-auxcop (warn): the same with a VBZ copula or auxiliary. Both are exempt when the subject has a nummod (measures: Three hours isn't far).

Sources. Fowler 1926, NUMBER §4; Zacharopoulos et al. (2023.emnlp-main.998); Wilson et al. (2023.scil-1.24); BLiMP (2020.tacl-1.25); ERRANT (P17-1074), W19-4406.

possessives-nmod-poss

Possessives — nmod:poss, always before the head

Gist. In English UD, possessive pronouns (my, your, his, their, whose) and the possessive 's are nmod:poss. A possessive pronoun is PRON with Poss=Yes, and the possessor always comes before what it possesses. English UD does not use det:poss (other languages do), but LLMs produce it.

Conditions and exceptions. A possessive as a conjunct (his and her) is conj. Independent mine, hers take other roles (nsubj, obj). a friend of mine is nmod with case of.

Examples. my office → nmod:poss(office, my); the president's office → nmod:poss(office, president), case(president, 's); whose car → nmod:poss(car, whose).

Machine-readable part. No rule here. The checks are rules en.nominal.prp-poss-rel (Possessive pronouns my, your, his, her, its, our, their) and en.nominal.poss-before-head (The possessor stands before the noun and is marked with 's).

Sources. UD guidelines en/dep/nmod-poss, en/dep/nmod, en/feat/Poss.

preposition-errors

Prepositions with verbs: depend on, discuss without about, arrive at

Gist. Prepositions are one of the most frequent learner error types (PREP). ERRANT distinguishes three kinds:

The preposition a verb takes is lexical knowledge that has to be stored per verb. In UD the error shows up as obl with the wrong case, or as obj where obl is needed.

Conditions and exceptions. depending on is a fixed expression. In arrived to find…, to is mark (purpose infinitive), not case, so it is not caught.

Examples. ✗ Depends of what you want.; ✗ We discussed about the plan.; ✗ I listen music.

Machine-readable part. en.errors.depend-on (warn): depend + obl whose case is not on/upon. en.errors.discuss-no-about (warn): discuss + about. en.errors.arrive-not-to (warn): arrive + to. en.errors.listen-to (warn): listen with an obj.

Sources. ERRANT (P17-1074, PREP); W19-4406; Koyama et al. (2025.acl-long.1026).

progressive-be-vbg

Progressive aspect: be + -ing

Gist. Non-passive auxiliary be (aux) requires the -ing form: is working. A base or finite form after be (✗ they are find, ✗ he is hate) is a text error (VERB:FORM) or a wrong annotation. The only legitimate "be + infinitive" is be to with the particle to (He was to leave at noon). EWT annotates was there as aux of the infinitive.

Conditions and exceptions. Passive be + VBN is aux:pass (see passive-structure). In is being done, is is aux, being is aux:pass, and the head is VBN.

Examples. ✗ they are find more interest in oil drilling; ✓ The United States was to cut its level.

Machine-readable part. en.errors.be-progressive (warn): a VERB tagged VB/VBD/VBZ/VBP with be as aux and no to mark.

Sources. ERRANT (P17-1074, VERB:FORM); UD guidelines en/dep/aux_; 2025.law-1.14.

pronoun-after-preposition

After a preposition — accusative: between you and me

Gist. A pronoun after a preposition is in the accusative (for me, with them), and so is the second member of a coordination: between you and me. The hypercorrection ✗ between you and I is an old error of educated speakers (Fowler also cites let you & I try). ERRANT classes it as PRON.

Conditions and exceptions. The check has two parts: a nominative pronoun with its own preposition, and a nominative pronoun that is a conjunct in a phrase whose preposition attaches to the first conjunct. It also catches wrong Case=Nom features on it in the gold standard.

Examples. ✗ between you and I → case(you, between), conj(you, I), I: Case=Nom; ✓ between you and me.

Machine-readable part. en.errors.nominative-after-preposition (warn): a Case=Nom personal pronoun with an ADP case. en.errors.nominative-conjunct-after-preposition (warn): a Case=Nom personal pronoun as conj of a word that has a preceding ADP case.

Sources. Fowler 1926, ME; UD guidelines en/feat/Case; ERRANT (P17-1074, PRON).

real-word-confusions

Confused words: there/their, to/too, then/than, where/were

Gist. The most frequent real-word errors in web text are homophones: their/there/they're, to/too, then/than, where/were, your/you're, its/it's. A spell checker misses them because each is a real word. EWT annotates such a word as the intended word and sets Typo=Yes: there used for their gets PRP$ and nmod:poss. So a form with another word's tag and no Typo=Yes is either a tagging error or a missing Typo mark.

Conditions and exceptions. Only unambiguous form + tag pairs are checked. Adverbial then (and then) and to as ADP/PART are legitimate. your/you're and its/it's involve tokenisation (multiword tokens) and are left out.

Examples. there car → there: PRP$, nmod:poss, Typo=Yes, CorrectForm=their; better then me → then: IN, case, Typo=Yes; it was to hot → to: ADV (RB), advmod, Typo=Yes.

Machine-readable part. en.errors.there-as-their (there/PRP$), en.errors.their-as-there (their/EX or RB), en.errors.to-as-too (to/ADV), en.errors.then-as-than (then/IN), en.errors.where-as-were (where/AUX). All are warn and require Typo=Yes.

Sources. EWT 2.18 practice (Typo=Yes + CorrectForm); Masciolini et al. (2025.udw-1.17); ERRANT (P17-1074); W19-4406.

relative-clause-agreement

The relative-clause verb agrees with the antecedent

Gist. When the relative pronoun (who, which, that) is the subject of the relative clause, the verb takes the number of the noun the clause attaches to: people who live, a man who lives. A mismatch means a text error, or that the clause was attached to the wrong noun (the servant of the actress who…).

Conditions and exceptions. In one of the best men that have ever lived, the antecedent is men, so the plural is correct (singular has is common but, per Fowler, a constant error). Collective nouns (the Taliban want) agree by meaning.

Examples. ✗ the people who lives here → ✓ live; ✓ He is one of the best men that have ever lived.

Machine-readable part. en.errors.relcl-plural-antecedent (warn): a plural antecedent, a PronType=Rel subject, and the relative verb is VBZ. en.errors.relcl-singular-antecedent (warn): a singular noun antecedent with a VBP relative verb. It is exempt for coordinated antecedents and for quantity or collective nouns.

Sources. Fowler 1926, NUMBER; Garcia et al. (2025.depling-1.4); BLiMP (2020.tacl-1.25); ICLE-RC (2025.law-1.16).

relative-pronoun-in-clause

The relative pronoun is inside the relative clause

Gist. Since UD 2.11, the relative pronoun (who, which, that) is a member of the relative clause (nsubj, obj, obl, …). It attaches to the clause's predicate, and the clause is acl:relcl of the antecedent. Relative that is PRON (WDT) with a role, not mark. mark that occurs only in complement clauses (the fact that he left). A pronoun attached directly to the antecedent means an inverted analysis.

Conditions and exceptions. Free relatives (whatever deal you want: whatever is det of deal) and nested relatives are exceptions. The rule only checks a pronoun that stands between the antecedent and the relative predicate.

Examples. the man who left → nsubj(left, who), acl:relcl(man, left); the book that I read → obj(read, that), that: PRON; the fact that he left → mark(left, that), acl(fact, left).

Machine-readable part. en.errors.relpron-inside-clause (warn): a PronType=Rel PRON attached to the antecedent, between it and the acl:relcl. The that-not-mark check is rule en.nominal.relative-that-not-mark in Relative that is a pronoun; no preposition precedes it.

Sources. 2023.udw-1.7; UD guidelines en/dep/acl-relcl, en/dep/mark; ICLE-RC (2025.law-1.16); Czerniak et al. (2025.tlt-1.12).

singular-subject-plural-verb

Singular subject with VBP

Gist. A singular noun subject requires VBZ: My wife knows, not know. VBP with a singular noun subject and no conjunct is a text agreement error or a wrong subject. A dropped third-person -s is among the most frequent errors of non-native writers.

Conditions and exceptions. These agree by meaning:

A coordinated subject (with conj) is skipped.

Examples. ✗ this dentist want to pull the tooth; ✗ The coffee taste burnt.; ✓ A lot of people say…

Machine-readable part. en.errors.singular-subject-vbp (warn): a singular NOUN/PROPN subject before a VBP verb, with no conj. en.errors.singular-subject-vbp-auxcop (warn): the same with a VBP copula or auxiliary. Both exempt quantity lemmas (lot, number, majority, rest, half, …) and collective lemmas (family, team, government, committee, staff, police, …).

Sources. ERRANT (P17-1074), W19-4406 (VERB:SVA); Fowler 1926, NUMBER; Wilson et al. (2023.scil-1.24); Hobbs et al. (2026.conll-main.7); Poutsma, GLME III ch. XXVI; Curme 1931.

subject-pronoun-case

The pronoun subject of a finite verb is nominative

Gist. The subject of a finite verb is nominative (I, he, she, we, they). ✗ Me and my family are moving, ✗ them came up with, ✗ her has a place are colloquial or learner forms. In non-finite constructions an accusative subject is normal (for me to sit in, him stuttering). So the check only applies to predicates with VerbForm=Fin.

Conditions and exceptions. Reflexives as subjects (Myself and Credit were calling) are also non-standard. A wrong Case=Acc on it in EWT is caught too.

Examples. ✗ Me and my family are moving.; ✓ It would be OK for me to sit in.; ✓ I remember him stuttering.

Machine-readable part. en.errors.finite-subject-nominative-auxcop (warn): a Case=Acc PRON subject before a finite copula or auxiliary. The verb-level check is rule en.nominal.finite-subject-nom in Case of the personal pronoun and its role in the sentence.

Sources. UD guidelines en/feat/Case; ERRANT (P17-1074, PRON); W19-4406; Poutsma, GLME IV ch. XXXII §8.

titles-and-company-suffixes

Titles (Mr., Dr.) and Inc. — nmod:desc

Gist. A title before a name (Mr., Dr., Professor) and a company suffix (Inc., Corp., Ltd., LLC) are optional descriptors: drop them and the name is still grammatical. Since UD 2.15 they are nmod:desc of the core name. Earlier they were flat or compound. flat is wrong because first and last name then do not form a constituent. Against compound: a title agrees in number (Presidents Obama and Biden), which compound dependents almost never do.

Conditions and exceptions. Co. 1691 ("company no. 1691") and Peters and Co. (a conjunct) are not descriptors, so Co. is excluded. A position with an article is appos (the president, Joe Biden). A regnal number (Elizabeth II) is flat.

Examples. Mr. Magoo → nmod:desc(Magoo, Mr.); Apple Inc. → nmod:desc(Apple, Inc.); JFK Jr. → nmod:desc(JFK, Jr.).

Machine-readable part. en.errors.title-desc (error): Mr./Mrs./Ms./Dr. (not a typo) right before a PROPN must be nmod:desc of it. en.errors.company-suffix-desc (warn): Inc./Corp./Ltd./LLC/PLC after a PROPN must be nmod:desc.

Sources. UD guidelines en/dep/nmod-desc; Schneider & Zeldes (2021.udw-1.14); 2023.udw-1.7.

tmod-npmod-unmarked

:tmod and :npmod merged into :unmarked (UD 2.15)

Gist. Bare nominal adverbials and modifiers (We met last year, five days before the funeral, $5 a share) were split into :tmod (time) and :npmod (other) until UD 2.15. Since 2.15, EWT and GUM use a single :unmarked subtype (obl:unmarked, nmod:unmarked). The old label comes from annotators trained on older releases, or from treebanks that keep the old scheme.

Conditions and exceptions. For ATIS, ESLSpok, CHILDES and LittlePrince, the old labels are their convention. Mova follows EWT 2.18, so for Mova they are errors. The CoNLL 2018 LAS metric ignores subtypes, so this difference does not affect LAS.

Examples. We met last year → obl:unmarked(met, year); IBM earned $5 a share → nmod:unmarked($, share); five days before the funeral → nmod:unmarked(funeral, days).

Machine-readable part. en.errors.tmod-npmod (error): any obl:tmod, obl:npmod, nmod:tmod, nmod:npmod.

Sources. UD guidelines en/dep/obl-unmarked, en/dep/nmod-unmarked, en/dep/nmod; UD issues #1028, #1094.

tough-vs-extraposition

"It is easy to X" and "X is easy to do" — different structure

Gist. Two similar sentences have different trees.

Conditions and exceptions. Tough adjectives: easy, hard, difficult, impossible, tough, simple, pleasant. too early to say is a different construction with too.

Examples. It is hard to say → expl(hard, It), csubj(hard, say); Fish are the easiest to take care of → nsubj(easiest, Fish), ccomp(easiest, take).

Machine-readable part. en.errors.extraposed-infinitive-csubj (warn): an ADJ with expl and a following to-infinitive, where the infinitive must be csubj. en.errors.tough-infinitive-not-csubj (warn): an ADJ with a nominal nsubj and a following to-infinitive, where the infinitive must not be csubj.

Sources. UD guidelines en/dep/csubj, en/dep/expl; BLiMP (2020.tacl-1.25, tough vs raising).

vernacular-style

Deliberate non-standard — Style, not Typo

Gist. EWT separates errors (Typo=Yes) from deliberate colloquial or dialect forms (Style=Vrnc, Coll, Slng):

An annotator that "corrects" these loses register information. One that misses have → of breaks the tree, because of becomes a preposition without a noun.

Conditions and exceptions. The line between a typo and a deliberate form is blurry: walkin, goin have both Style=Vrnc and Typo=Yes in EWT.

Examples. he should of called back → of: AUX, lemma have, VB, Style=Vrnc, aux(called, of); them apples → them: DT, det, Style=Vrnc.

Machine-readable part. en.errors.of-have-vernacular (warn): of as AUX must have lemma have and Style=Vrnc. en.errors.them-det-vernacular (warn): them as det must have Style=Vrnc.

Sources. EWT 2.18 practice (Style feature); Masciolini et al. (2025.udw-1.17).

vp-ellipsis-aux-head

VP ellipsis: the auxiliary becomes the head

Gist. In John will win gold and Mary will too, the second will has lost its verb. Basic UD has no empty nodes, so the auxiliary becomes the head of the second clause: conj(win, will₂), nsubj(will₂, Mary). A wrong analysis attaches will₂ as aux of the first win. That gives a long backward arc and an auxiliary after its head, which never happens in ordinary clauses.

Conditions and exceptions. Inversion with a fronted participle or gerund: Attached is the file (an aux:pass, not checked), Sailing with the Roosevelt is…, Compounding this is…. orphan is not used in VP ellipsis.

Examples. He can swim and I can too → conj(swim, can₂), nsubj(can₂, I); ✗ aux(swim, can₂).

Machine-readable part. en.errors.aux-before-verb (warn): an aux that follows its VERB head.

Sources. UD guidelines en/dep/orphan ("In VP-ellipsis, we keep the auxiliary as the head"); Corbetta et al. (2025.tlt-1.6); Kellert et al. (2025.findings-emnlp.863); 2025.law-1.14.

xcomp-no-subject

xcomp has no subject of its own

Gist. xcomp is an open complement: its subject comes from the main clause through control or raising (I want to leave, She seems happy). A complement with its own subject is closed, so it is ccomp (I know that he left, He said he would go). Parsers often confuse xcomp and ccomp.

Conditions and exceptions. With object control, the object belongs to the main verb, not to the xcomp (I want him to go → obj(want, him), xcomp(want, go)). A for-clause (for him to go) has nsubj in EWT and so is not xcomp.

Examples. I want to go → xcomp(want, go); They made him leave → obj(made, him), xcomp(made, leave); He said he would go → ccomp(said, go), nsubj(go, he).

Machine-readable part. en.errors.xcomp-no-subject (warn): xcomp with an nsubj/nsubj:pass dependent.

Sources. UD guidelines en/dep/xcomp, en/dep/ccomp; BLiMP (2020.tacl-1.25, control/raising); de Marneffe & Manning 2008 (W08-1301).

This page in Markdown → https://md.mova.elamur.ai/free/en/docs/repo-docs/seeds/en-seeds-errors/