A French dictionary contains roughly 60,000 entries, but a French speaker does not memorize 60,000 words. They memorize a smaller set of roots and a system of rules for building new words from them. Once you know the rules, décongelable is not a new word — it is dé- (undo) + congel(er) (freeze) + -able (capable of being). Unfreeze-able. Defrostable. You decoded a word you had never seen.
This page surveys the French word-formation system end to end. It is the map for the detailed pages on individual prefixes and suffixes. The investment is high-leverage: a few weeks of work on word-formation patterns expands your passive vocabulary by an order of magnitude.
The four mechanisms
French word-formation operates through four main processes, and most complex words combine more than one of them.
- Prefixation — add a meaningful element to the front of a word. Faire (do) → refaire (redo), défaire (undo), parfaire (perfect), contrefaire (counterfeit).
- Suffixation — add a meaningful element to the end of a word, often changing its part of speech. Nation (n.) → national (adj.) → nationalité (n.) → nationaliser (v.) → nationalisation (n.).
- Composition (compounding) — combine two existing words into one. Porte-monnaie (carry-money = wallet), sous-marin (under-sea = submarine), arc-en-ciel (bow-in-sky = rainbow).
- Conversion (zero-derivation) — use a word in a different grammatical role without altering its form. The infinitive manger becomes the noun le manger (the food/eating); the adjective jeune becomes the noun un jeune (a young person).
The first two are by far the most productive. A working knowledge of the main prefixes and suffixes unlocks most of the vocabulary you will encounter in newspapers, academic prose, and conversation.
Prefixes: the core inventory
A prefix changes or refines the meaning of the base word without changing its part of speech. Faire is a verb; refaire, défaire, parfaire are all still verbs. Possible is an adjective; impossible is still an adjective.
| Prefix | Meaning | Examples |
|---|---|---|
| re- / ré- / r- | again, back | refaire, redire, rouvrir, réécrire, revenir |
| dé- / dés- | undo, reverse, remove | défaire, désordre, déshabiller, démonter |
| in- / im- / il- / ir- | not (negation) | incompréhensible, impossible, illégal, irréel |
| mal- / mé- / més- | badly, wrongly | malheureux, malhonnête, méfiance, mésentente |
| anti- | against, counter | antibiotique, antivol, antibrouillard, antimite |
| pré- | before | prévoir, prévenir, préhistoire, préchauffer |
| post- | after | postdater, postopératoire |
| sur- | over, excessive | surcharger, surestimer, surpopulation |
| sous- | under, insufficient | sous-estimer, sous-payer, sous-titre, sous-marin |
| co- | together, jointly | cohabiter, coauteur, copropriétaire |
| auto- | self | autodidacte, autoportrait, autodéfense |
| extra- | outside, beyond | extraordinaire, extraterrestre, extrascolaire |
| inter- | between | international, interurbain, intervenir |
| trans- | across | transporter, transatlantique, transformer |
| en- / em- | into, cause to be | encourager, emporter, embarquer, enfermer |
Il faut prévoir un budget pour les imprévus, c'est essentiel.
You have to plan a budget for unforeseen expenses — it's essential.
L'écharpe est antimite, tu peux la ranger dans l'armoire.
The scarf is moth-proof — you can put it away in the wardrobe.
Nous sommes coauteurs de ce rapport, il ne faut pas oublier son nom.
We are co-authors of this report — we mustn't forget his name.
Le sous-titre du film est en français, tu peux le lire facilement.
The film's subtitles are in French — you can read them easily.
For deep treatment, see word-formation/prefix-re, word-formation/prefix-de-and-des, and word-formation/prefix-in-im-il-ir.
Suffixes: the inventory by output category
A suffix usually changes the part of speech: a verb becomes a noun, a noun becomes an adjective, an adjective becomes a noun again. Native speakers compose these transformations fluently, often chaining several suffixes in a single word.
Verb → noun
| Suffix | Meaning | Examples |
|---|---|---|
| -tion / -sion | the act or result of V-ing (feminine) | création, révolution, décision, action, discussion |
| -ment | the act or result of V-ing (masculine) | changement, gouvernement, enseignement, bâtiment |
| -age | the act or process of V-ing (masculine) | passage, démarrage, recyclage, mariage, lavage |
| -ure | the result or product of V-ing (feminine) | écriture, peinture, lecture, fermeture, signature |
| -eur / -euse | the agent who V-s | chanteur/chanteuse, vendeur/vendeuse, danseur/danseuse |
Le gouvernement a annoncé une décision importante ce matin.
The government announced an important decision this morning.
Le recyclage du plastique reste un défi pour les municipalités.
Plastic recycling remains a challenge for municipalities.
C'est une chanteuse incroyable, je l'ai vue en concert l'année dernière.
She's an incredible singer — I saw her in concert last year.
The gender of -tion, -sion, -ure (feminine) and -ment, -age (masculine) is regular. Learning the suffix grammatically pins the gender — a small but useful shortcut.
Adjective → noun (abstract quality)
| Suffix | Meaning | Examples |
|---|---|---|
| -ité | the quality of being X (feminine) | nationalité, possibilité, identité, qualité, sécurité |
| -isme | doctrine, system, condition (masculine) | capitalisme, socialisme, féminisme, optimisme |
| -esse | quality, state (feminine) | jeunesse, richesse, tristesse, faiblesse, politesse |
| -eur | abstract quality (feminine) | douceur, grandeur, lenteur, lourdeur |
| -ie | condition, behavior (feminine) | jalousie, courtoisie, modestie, économie |
La qualité de l'air en ville s'est dégradée ces dernières années.
Air quality in the city has deteriorated in recent years.
Sa jeunesse explique en partie son optimisme.
Her youth partly explains her optimism.
Note the trap: -eur as agent suffix is masculine (un chanteur), but -eur as abstract-quality suffix is feminine (la douceur, la grandeur). You learn this gender pair by pair.
Noun → adjective
| Suffix | Meaning | Examples |
|---|---|---|
| -al / -elle | relating to X | national, royal, original, culturel, naturel |
| -aire | relating to X | solaire, lunaire, universitaire, alimentaire |
| -eux / -euse | full of X, characterized by X | heureux, dangereux, courageux, paresseux |
| -if / -ive | tending to X | actif, attentif, sportif, créatif, expressif |
| -ique | relating to X (often technical) | économique, politique, historique, scientifique |
| -able / -ible | capable of being V-ed | mangeable, lisible, faisable, visible, incroyable |
Ce restaurant propose des plats végétariens et sans gluten, c'est rare et bienvenu.
This restaurant offers vegetarian and gluten-free dishes — it's rare and welcome.
Ton idée est intéressante mais elle n'est pas faisable cette année.
Your idea is interesting but it's not feasible this year.
Adjective → adverb
This is the most regular pattern in French word-formation:
- Most adjectives: feminine form + -ment. Lent → lente → lentement (slowly). Doux → douce → doucement (gently).
- Adjectives ending in -ant: replace with -amment. Constant → constamment.
- Adjectives ending in -ent: replace with -emment. Récent → récemment. (Both -amment and -emment are pronounced /amɑ̃/.)
- A few irregular: bon → bien (well, not bonnement), mauvais → mal (badly), meilleur → mieux.
Parle-moi doucement, le bébé dort.
Speak to me gently — the baby is sleeping.
Il a récemment changé de travail, il est très content.
He recently changed jobs and he's very happy.
Verb → adjective: -able
The -able suffix is highly productive — attached to almost any transitive verb, it creates an adjective meaning "capable of being V-ed."
Cette voiture est encore réparable, on peut sauver le moteur.
This car is still repairable — we can save the engine.
C'est buvable ? J'ai mis trop de sucre.
Is it drinkable? I put in too much sugar.
When dé- is added to an -able adjective, the result negates: défaisable, décongelable, démontable. With the in- negative prefix and -able, you get the very productive pattern incomparable, impossible, imprévisible, incontournable.
See word-formation/suffix-tion-and-ment, word-formation/suffix-eur-euse, and word-formation/suffix-able for deeper treatment.
Compounding: when two words become one
French compounds are mostly hyphenated, and they fall into two main types.
Verb-noun compounds (agent or instrument)
A verb stem fused with a noun, naming the instrument or agent that performs the action:
| Compound | Literal | Meaning |
|---|---|---|
| porte-monnaie | carry-money | wallet, coin purse |
| porte-clés | carry-keys | keychain |
| essuie-glace | wipe-pane | windshield wiper |
| ouvre-boîte | open-can | can opener |
| tire-bouchon | pull-cork | corkscrew |
| lave-vaisselle | wash-dishes | dishwasher |
| lave-linge | wash-laundry | washing machine |
| sèche-cheveux | dry-hairs | hairdryer |
| gratte-ciel | scratch-sky | skyscraper |
These compounds are masculine and their pluralization is notoriously irregular. The 1990 spelling reform simplified things: most verb-noun compounds now take a final -s on the noun in the plural and nowhere else (un porte-clé, des porte-clés; un essuie-glace, des essuie-glaces). But traditional spellings persist (porte-monnaie is often invariable in both numbers), so dictionary checking is wise.
J'ai oublié mon porte-monnaie au café, j'espère qu'il y est encore.
I forgot my wallet at the café — I hope it's still there.
Les essuie-glaces ne marchent plus, je vais les changer demain.
The windshield wipers don't work anymore — I'll change them tomorrow.
Noun-preposition-noun compounds
A noun with a prepositional modifier, frozen as a single lexical unit:
| Compound | Literal | Meaning |
|---|---|---|
| arc-en-ciel | arch-in-sky | rainbow |
| pomme de terre | apple of earth | potato |
| chemin de fer | way of iron | railway |
| chef-d'œuvre | chief of work | masterpiece |
| après-midi | after-noon | afternoon |
Pluralization is, again, irregular: arcs-en-ciel, pommes de terre, chefs-d'œuvre. Only the first noun pluralizes.
On a vu un arc-en-ciel magnifique après l'orage.
We saw a beautiful rainbow after the storm.
Ce roman est un chef-d'œuvre, je l'ai lu trois fois.
This novel is a masterpiece — I've read it three times.
See word-formation/compounds for the full pluralization rules.
Conversion: same form, different role
French uses any infinitive as a noun by adding the article le: le manger (eating, food), le boire (drinking), le savoir (knowledge), le pouvoir (power), le devoir (duty, homework). These nouns are masculine and behave like ordinary nouns.
Le savoir-vivre est une qualité française difficile à définir.
Savoir-vivre — knowing how to behave — is a French quality that's hard to define.
Il faut respecter le pouvoir judiciaire, c'est un principe fondamental.
One must respect the judicial branch — it's a fundamental principle.
Adjectives also convert to nouns freely: un jeune (a young person), les pauvres (the poor), les riches (the rich), le beau (beauty, the beautiful), le vrai (truth, the true). This is especially common in abstract or philosophical discourse.
Why this matters for a learner
The honest truth: French has the most regular word-formation system of any major European language, and English speakers are unusually well-positioned to exploit it, because the same Latin roots appear in English with similar suffixes. Nation/national/nationality in English is nation/national/nationalité in French — three words for the price of one. Govern/government/governmental maps to gouverner/gouvernement/gouvernemental.
The trap is that the patterns are productive in different directions. English doubled -ation freely; French allows -tion but constrains where it can be added. Argumentation exists in both languages, but organize → organization in English is organiser → organisation in French (one -s-, not a z). And some patterns exist in one language but not the other: French -ité maps to English -ity (nationality, identity, possibility) but does not map to anything like -ment in English — changement is just change in English. The mapping requires attention to detail.
Common Mistakes
Mistake 1: Assuming English suffixes map directly to French.
❌ Le développeur a écrit un nouveau softwarisation.
No such word. English -ization is sometimes -isation in French, but not all English words have a French equivalent — especially recent neologisms.
✅ Le développeur a écrit un nouveau logiciel.
The developer wrote new software.
Mistake 2: Confusing the two senses of -eur: agent (masculine) vs abstract (feminine).
❌ Le grandeur du roi était impressionnante.
'Grandeur' (greatness) is the abstract noun, feminine. The agent suffix '-eur' (le chanteur, le danseur) is masculine, but the abstract '-eur' (la grandeur, la douceur) is feminine.
✅ La grandeur du roi était impressionnante.
The greatness of the king was impressive.
Mistake 3: Misspelling the re- prefix before vowels.
❌ Je vais reécrire le rapport ce soir.
Before a vowel, the prefix usually takes the form ré- (with accent) or contracts to r- in established forms.
✅ Je vais réécrire le rapport ce soir.
I'm going to rewrite the report tonight.
Mistake 4: Failing to pluralize the first noun in compound nouns.
❌ Nous avons vu plusieurs arc-en-ciels après la pluie.
In noun-preposition-noun compounds, only the first noun pluralizes: arcs-en-ciel.
✅ Nous avons vu plusieurs arcs-en-ciel après la pluie.
We saw several rainbows after the rain.
Mistake 5: Assuming all verbs accept all prefixes.
❌ Je voudrais désaller au cinéma.
The dé- prefix attaches productively but not to all verbs. 'Désaller' does not exist; the meaning 'unmove' or 'undo a trip' would be expressed differently.
✅ Je voudrais annuler ma sortie au cinéma.
I'd like to cancel my cinema outing.
Key takeaways
- French builds new words through prefixation, suffixation, compounding, and conversion. Prefixation and suffixation do most of the work.
- The main prefixes are re- (again), dé-/dés- (undo), in-/im-/il-/ir- (not), pré- (before), anti- (against), and a handful of others. They preserve the part of speech.
- Suffixes typically change the part of speech and pin the gender: -tion/-sion (f.), -ment (m.), -age (m.), -ure (f.), -eur (agent m. / abstract f.), -ité (f.), -isme (m.).
- Compounds (verb-noun, noun-prep-noun) are hyphenated and have irregular plural rules. Only certain elements pluralize.
- Conversion turns infinitives into masculine nouns (le savoir, le pouvoir) and adjectives into nouns (un jeune, les pauvres).
- Decompose new words: prefix + stem + suffix. The habit doubles reading speed within weeks.
Now practice French
Reading grammar gets you part of the way. The exercises are where it sticks — free, no signup needed.
Start learning French→Related Topics
- Le Préfixe Re-: répétitionB1 — The French prefix re- (also ré- before vowels and r- in established forms) is one of the most productive word-formation tools in the language. It attaches to almost any verb to mean 'do again' or 'do back' — refaire, redire, revoir, relire, reprendre. Knowing the spelling rules and the two senses unlocks hundreds of common words.
- Les Préfixes Dé- et Dés-: négation/séparationB1 — The dé-/dés- prefix reverses or removes an action: faire → défaire (undo), ordre → désordre (disorder), habiller → déshabiller (undress). The choice between dé- and dés- is phonological — dés- before vowels, dé- before consonants — and the prefix attaches to verbs, nouns, and adjectives alike.
- Les Préfixes In-, Im-, Il-, Ir-: négationB1 — The negative prefix in- (and its assimilated forms im-, il-, ir-) attaches to adjectives and a few nouns to produce the opposite meaning: possible/impossible, légal/illégal, réel/irréel, compréhensible/incompréhensible. The choice among the four forms is purely phonological — the consonant of the prefix assimilates to whatever follows.
- Les Suffixes -tion et -ment: noms abstraitsB1 — The suffixes -tion and -ment are the two great factories of abstract nouns in French. -tion derives feminine nouns from verbs (déclarer → déclaration); -ment derives masculine nouns from verbs (changer → changement). Mastering the pair gives you instant access to thousands of words and a reliable shortcut for predicting gender.
- Les Suffixes -eur/-euse: agent et qualitéB1 — The pair -eur/-euse turns verbs into agent nouns naming a person who does the action (vendeur/vendeuse, travailleur/travailleuse) and turns adjectives into abstract nouns naming the corresponding quality (haut → hauteur, large → largeur). A separate -teur/-trice pair, inherited from Latin, covers learned formations like acteur/actrice.
- Les Mots ComposésB2 — French builds compound nouns in two main ways: hyphenated combinations like porte-monnaie (verb + noun), sous-marin (preposition + adjective), arc-en-ciel (lexicalized phrase), and chef-d'œuvre (noun + de + noun); and lexicalized phrases without hyphens like pomme de terre and chemin de fer. The plural rules look intimidating but reduce to one principle: only nouns and adjectives can take a plural mark — verbs, prepositions, and adverbs always stay invariable.
- La Dérivation Verbale: -iser, -ifierB2 — French derives new verbs from adjectives and nouns through two productive suffixes: -iser (moderniser, optimiser, finaliser) and -ifier (simplifier, justifier, qualifier). Both yield first-group -er verbs and combine readily with -ation / -ification to give their nominal partners. -iser is especially productive in modern technical and corporate French.