FlexiLingoIn one line
In a compound noun only nouns and adjectives take a plural — verbs, adverbs and prepositions never do.
The table
| Structure | Plural | Example | Pronunciation |
|---|---|---|---|
| noun + noun | both | des choux-fleurs | /de ʃu.flœʁ/ |
| noun + adjective | both | des coffres-forts | /de kɔfʁ.fɔʁ/ |
| adjective + noun | both | des grands-parents | /de ɡʁɑ̃.pa.ʁɑ̃/ |
| verb + noun | the noun only, if it makes sense | des ouvre-boîtes | /de.z‿uvʁ.bwat/ |
| verb + verb | neither | des laissez-passer | /de lɛ.se.pa.se/ |
| adverb + noun | the noun only | des arrière-boutiques | /de.z‿a.ʁjɛʁ.bu.tik/ |
| preposition + noun | the noun only | des après-midi — invariable | /de.z‿a.pʁɛ.mi.di/ |
| a whole clause | invariable | des on-dit | /de.z‿ɔ̃.di/ |
The rule underneath: only something that can inherently be plural becomes plural. Verbs, adverbs and prepositions cannot.
English compounds pluralise the head noun and leave everything else alone — passers-by, attorneys-general, bottle-openers. French does the same thing in principle, but it hyphenates far more of them and pluralises adjectives as well, which English never does:
des grands-parentshas anson both words.
Common compound nouns
| Noun | Gender | Plural |
|---|---|---|
le grand-père /lə ɡʁɑ̃.pɛʁ/ | masculine | les grands-pères /le ɡʁɑ̃.pɛʁ/ |
la grand-mère /ɡʁɑ̃ mɛʁ/ | feminine | les grands-mères /le ɡʁɑ̃.mɛʁ/ |
le chef-d'œuvre /lə ʃe.døvʁ/ | masculine | les chefs-d'œuvre /le ʃɛf.dœvʁ/ |
le porte-monnaie /lə pɔʁt.mɔ.nɛ/ | masculine | les porte-monnaie /le pɔʁt.mɔ.nɛ/ |
le sac à dos /lə sak a do/ | masculine | les sacs à dos /le sakz a dɒs/ |
le tire-bouchon /lə tiʁ.bu.ʃɔ̃/ | masculine | les tire-bouchons /le tiʁ.bu.ʃɔ̃/ |
l'après-midi /la.pʁɛ.mi.di/ | masculine or feminine | les après-midi /le.z‿a.pʁɛ.mi.di/ |
le rez-de-chaussée /ʁed.ʃo.se/ | masculine | les rez-de-chaussée /le ʁe.də.ʃo.se/ |
le gratte-ciel /lə ɡʁat.sjɛl/ | masculine | les gratte-ciel /le ɡʁat.sjɛl/ |
le coup d'œil /lə ku dœj/ | masculine | les coups d'œil /le ku dœj/ |
la pomme de terre /pɔm də tɛʁ/ | feminine | les pommes de terre /le pɔm də tɛʁ/ |
le timbre-poste /lə tɛ̃bʁ.pɔst/ | masculine | les timbres-poste /le tɛ̃bʁ.pɔst/ |
le week-end /lə wi.kɛnd/ | masculine | les week-ends /le wi.kɛndz/ |
le lave-vaisselle /lav.vɛ.sɛl/ | masculine | les lave-vaisselle /le lav.vɛ.sɛl/ |
l'ouvre-boîte /luvʁ.bwat/ | masculine | les ouvre-boîtes /le.z‿uvʁ.bwat/ |
The "does it make sense" question in verb + noun
If the noun is inherently singular, it stays singular even in the plural form:
| Why | |
|---|---|
un porte-monnaie | a money-carrier — monnaie is uncountable |
un gratte-ciel | a sky-scraper — there is only one sky |
un porte-avions | an aircraft carrier — it carries several aircraft |
un essuie-glace | a windscreen wiper |
The 1990 spelling reform simplified this: it allows every such noun to take an
sin the plural —des porte-monnaies. Both forms are accepted today.
Gender — which part it comes from
| Structure | Gender from | Pronunciation |
|---|---|---|
| noun + noun | the first part — un timbre-poste is masculine because timbre is | /œ̃ tɛ̃bʁ.pɔst/ · /tɛ̃bʁ/ |
| noun + preposition + noun | the first part — une pomme de terre is feminine | /yn pɔm də tɛʁ/ |
| verb + noun | always masculine — un ouvre-boîte un porte-monnaie | /œ̃.n‿uvʁ.bwat/ · /œ̃ pɔʁt.mɔ.nɛ/ |
| adverb/preposition + noun | usually the second part |
A verb + noun compound is always masculine, even when the second noun is feminine:
un ouvre-bouteilleis masculine althoughbouteilleis feminine.
grand-mère — a historical irregularity
Why does grand not go feminine in grand-mère?
Because in Old French grand had only one form and was used for both genders. grand-mère is a survival from that period.
And its plural is disputed:
| Pronunciation | ||
|---|---|---|
des grands-mères | common today | /de ɡʁɑ̃.mɛʁ/ |
des grand-mères | the traditional form | /de ɡʁɑ̃.mɛʁ/ |
Both are accepted.
Without a hyphen — the unwritten compounds
Some combinations have no hyphen but are still a unit:
| Plural | |
|---|---|
une salle de bains /yn sal də bɛ̃/ | des salles de bains /de sal də bɛ̃/ |
un chemin de fer /œ̃ ʃə.mɛ̃ də fɛʁ/ | des chemins de fer /de ʃə.mɛ̃ də fɛʁ/ |
une carte de crédit /yn kaʁt də kʁe.di/ | des cartes de crédit /de kaʁt də kʁe.di/ |
un coup de main /œ̃ ku də mɛ̃/ | des coups de main /de ku də mɛ̃/ |
Only the first part goes plural, because the second describes the type rather than counting an object. English does the same with "cups of tea", "pieces of furniture".
Examples
| English | French | Pronunciation |
|---|---|---|
| My grandfathers. | Mes grands-pères. | /me ɡʁɑ̃ pɛʁ/ |
| My grandmother. | Ma grand-mère. | /ma ɡʁɑ̃ mɛʁ/ |
| The potatoes. | Les pommes de terre. | /le pɔm də tɛʁ/ |
| My wallet. | Mon porte-monnaie. | /mɔ̃ pɔʁt mɔ.nɛ/ |
| The rucksacks. | Les sacs à dos. | /le sa.k‿a do/ |
| The afternoons. | Les après-midi. | /le.z‿a.pʁɛ mi.di/ |
| The skyscrapers. | Les gratte-ciel. | /le ɡʁat sjɛl/ |
| The weekends. | Les week-ends. | /le wi.kɛnd/ |
| The dishwasher. | Le lave-vaisselle. | /lə lav vɛ.sɛl/ |
| The bathrooms. | Les salles de bains. | /le sal də bɛ̃/ |
Common mistakes
| ❌ | ✅ | Why |
|---|---|---|
des ouvres-boîtes | des ouvre-boîtes | A verb does not go plural |
des après-midis | des après-midi | Preposition + invariable noun |
des salle de bains | des salles de bains | The first part goes plural |
une grande-mère | une grand-mère | The historical form |
des gratte-ciels | des gratte-ciel | There is only one ciel |
des chef-d'œuvres | des chefs-d'œuvre | The first part goes plural |
Why this rule is so untidy
because nobody designed it
French compound nouns were built piecemeal over a thousand years — each one in its own era, with the logic of that era.
And nobody ever sat down to write a single rule. What we now call "the rule" is a description written after the fact, an attempt to impose order on something that was never orderly.
The 1990 spelling reform tried to tidy it:
| Proposal | Outcome |
|---|---|
every noun takes s in the plural | partly accepted |
| some hyphens removed | porte-monnaie → portemonnaie — barely accepted |
In practice both forms are correct today and neither is marked wrong in an exam.
English is no better and you already know it. Passers-by but bottle-openers; attorneys-general but court-martials; mother-in-laws and mothers-in-law both circulate. Nobody learns these from a rule either.
The practical point: this is the lowest-yield corner of French spelling. Do not memorise the list — learn twenty common compounds with their plurals and look up the rest when you meet them.
And if you are stuck in an exam, apply the general rule:
Nouns and adjectives go plural. Verbs, adverbs and prepositions do not.
That is right almost every time.