Plural of compound nouns: sons-in-law, passers-by, forget-me-nots

Gist. In a compound noun the plural usually goes on the head word — the one that names the thing. If the head comes first, followed by a prepositional phrase or an adverb, the -s ends up inside: son-in-law → sons-in-law, passer-by → passers-by, hanger-on → hangers-on, commander-in-chief → commanders-in-chief. If there is no head noun (the word describes the bearer of a property), the -s goes at the end: forget-me-nots, go-betweens, grown-ups, redcoats, runaways.

Conditions and exceptions.

• Noun + adjective after it: bookish courts-martial, attorneys general, colloquial court-martials.
• Handful, spoonful, mouthful are no longer felt as compounds: handfuls, spoonfuls (less often spoonsful).
• Compounds with -man: Englishmen, policemen (see noun-plural-mutation-en).
• In colloquial speech the -s sometimes moves to the end: son-in-laws.
• A hyphenated compound in EWT is usually one token; then the tag is NNS, Number=Plur, and the lemma is the singular of the whole compound (sons-in-law → son-in-law).

Examples. my sisters-in-law; the passers-by; the runners-up; two forget-me-nots.

In UD. NOUN, NNS, Number=Plur; lemma — the compound in the singular (passers-by → passer-by).

Sources. Sweet NEG I §1018–1019 (text-1, p. 349: hangers-on, fathers-in-law, commanders-in-chief; go-betweens, forget-me-nots; courts-martial / court-martials), §440–442 (p. 183–184: group compounds son-in-law, plural sons-in-law); Whitney §130 (text-1, p. 74: merchantmen, brothers-in-law, hangers-on; redcoats, turnkeys, runaways, forget-me-nots; mouthfuls, handfuls); Jespersen MEG II 2.3₁ (text-2, p. 52: usually only the last element changes; sons-in-law, lookers-on), VI 17.8 (text-5, p. 314–316: drawbacks, grown-ups, forget-me-nots, handfuls); Kruisinga II.2 §§763–773 (text-3, p. 29–35).

rule: en.morph.compound-plural-lemma
what: sons-in-law, passers-by etc. — plural, lemma is the compound in the singular
match: n[upos=NOUN, form=mothers-in-law|fathers-in-law|sons-in-law|daughters-in-law|brothers-in-law|sisters-in-law|passers-by|lookers-on|hangers-on|runners-up|commanders-in-chief|attorneys-general|courts-martial, !feats.Typo]
require: n[xpos=NNS, feats.Number=Plur, lemma=mother-in-law|father-in-law|son-in-law|daughter-in-law|brother-in-law|sister-in-law|passer-by|looker-on|hanger-on|runner-up|commander-in-chief|attorney-general|court-martial]
severity: warn
source: Sweet NEG I §1018–1019, §440–442; Whitney §130

This page in Markdown → https://md.mova.elamur.ai/free/en/docs/en/seeds/morph/noun-plural-compounds/