📚 French Grammar Lesson: Understanding and Forming the Plural of French Compound Nouns
Compound nouns in French can be confusing—especially when it comes to making them plural. Unlike English, French plurals of compound nouns don’t always follow a single rule. Instead, they depend on the grammar role and part of speech of each component.
Let’s break it down step by step.
✅ What Is a Compound Noun?
A compound noun (un nom composé) is a noun made up of two or more words that form a single idea.
Example:
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un porte-monnaie = a wallet
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un chou-fleur = a cauliflower
🧠 The 3 Golden Rules of Plural Formation
When forming the plural, consider:
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The function of each word (noun, verb, adjective, etc.)
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Whether the word is invariable
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What part(s) of speech can take a plural “s”
Let’s look at the most common cases:
📗 Case-by-Case Plural Rules
1. Noun + Adjective
➡️ Both take an “s” in the plural.
| Singular | Plural |
|---|---|
| un coffre-fort | des coffres-forts |
| un chou-fleur | des choux-fleurs |
| un timbre-poste | des timbres-poste ❌ (poste is invariable here) |
🔍 Note: Some exceptions exist depending on whether the second word is still meaningful.
2. Verb + Noun (object of the verb)
➡️ Only the noun takes the plural.
| Singular | Plural |
|---|---|
| un tire-bouchon | des tire-bouchons |
| un porte-clé | des porte-clés |
| un coupe-ongle | des coupe-ongles |
🎯 Logic: The verb doesn’t change; only the object (noun) becomes plural.
3. Noun + Noun (connected with a hyphen)
➡️ Both nouns take an “s”, if both are countable and meaningful.
| Singular | Plural |
|---|---|
| un oiseau-mouche | des oiseaux-mouches |
| un chou-fleur | des choux-fleurs |
🔍 If the second noun acts like a complement and not a real noun on its own, it stays invariable:
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un chef-d’œuvre → des chefs-d’œuvre ✅
4. Preposition + Noun / Noun + Preposition + Noun
➡️ Usually only the noun(s) take the plural.
| Singular | Plural |
|---|---|
| un arc-en-ciel | des arcs-en-ciel |
| un pomme de terre | des pommes de terre |
| un verre à vin | des verres à vin |
📌 Prepositions: “de”, “à”, “en”, etc. do not change.
5. Invariable Words
➡️ Some compound nouns are always invariable.
| Singular | Plural |
|---|---|
| un après-midi | des après-midi |
| un sans-abri | des sans-abri |
| un gratte-ciel | des gratte-ciel |
🧪 Test Yourself: Quiz Time
Which of these is the correct plural?
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un porte-bonheur
a) des portes-bonheurs
b) des porte-bonheurs ✅ -
un chef-lieu
a) des chefs-lieux ✅
b) des chefs-lieu -
un tire-lait
a) des tires-laits
b) des tire-laits ✅
✍️ Summary Table
| Structure | Plural Rule | Example |
|---|---|---|
| Noun + adjective | Pluralize both | un chou-fleur → des choux-fleurs |
| Verb + noun | Pluralize noun only | un tire-bouchon → des tire-bouchons |
| Noun + noun | Pluralize both if meaningful | un oiseau-mouche → des oiseaux-mouches |
| Preposition + noun | Pluralize nouns only | un arc-en-ciel → des arcs-en-ciel |
| Fixed/invariable compound | No change | un sans-abri → des sans-abri |
💬 Final Tips
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Always check a good dictionary if you’re unsure—many compound nouns are exceptions.
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Use context to determine whether words are acting as adjectives, verbs, or nouns.
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Don’t worry—even native speakers get confused sometimes with these!
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