French Adjective Agreement Mistakes to Avoid

French adjectives agree in gender and number with the noun they describe. Most mistakes come from forgetting the feminine -e, mishandling plural forms, or using an irregular masculine form as the feminine. Once you check the noun first, the adjective becomes much more predictable.

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The core distinction: gender and number, not meaning

French adjectives change form to match the noun they modify. English adjectives stay invariable, so English speakers often treat French adjectives as fixed words. In French, petit becomes petite before a feminine noun, and both forms take -s in the plural.

• un petit garçon a small boy
• une petite fille a small girl
• des petits garçons small boys
• des petites filles small girls

This agreement applies even when the adjective comes after the noun, as in un livre intéressant an interesting book and une histoire intéressante an interesting story. The noun controls the ending, not the adjective’s position or the English translation.

The most frequent mistakes, with fixes

Try not to see these as separate rules. They all come from the same habit: not checking the noun first.

1. Forgetting the feminine -e

Many learners write une petit fille instead of une petite fille. The masculine form petit cannot describe a feminine noun. Add -e to form the feminine for most adjectives: grand / grande, joli / jolie, content / contente.

2. Making the plural more complicated than it is

French plural adjectives usually add -s: des murs gris grey walls, des fleurs rouges red flowers. Some masculine adjectives ending in -s or -x stay the same in the masculine plural: un homme gros / des hommes gros, un air heureux / des airs heureux. The feminine forms still change: une femme grosse / des femmes grosses.

3. Using the masculine singular as a default

After être, adjectives agree with the subject. If the subject is feminine plural, the adjective must be feminine plural: Elles sont fatiguées. They are tired. Ils sont fatigués. They are tired. The English sentence gives no clue, so the French subject matters.

4. Forgetting irregular feminine forms

Some high-frequency adjectives do not simply add -e. Beau becomes belle, nouveau becomes nouvelle, vieux becomes vieille, blanc becomes blanche, and bon becomes bonne. Saying une beau maison instead of une belle maison is a common slip.

5. Getting mixed-gender plurals wrong

When an adjective describes a group with at least one masculine noun, French uses the masculine plural form: un garçon et une fille intelligents. This can feel unfair, but it is the standard pattern. Some pairs are not agreement mistakes but lexical confusions; for more on that, see French words easy to confuse.

Examples in context: agreement you can hear

Listening helps you catch endings you might skip when reading. These pairs show the same adjective moving across gender and number.

Phrase	English
un problème important	an important problem
une question importante	an important question
des problèmes importants	important problems
des questions importantes	important questions

Notice how the final consonant of important is silent in the masculine singular but pronounced in the feminine singular: important /ɛ̃.pɔʁ.tɑ̃/ vs importante /ɛ̃.pɔʁ.tɑ̃t/. The feminine form often makes the final consonant audible, which is a useful listening cue. Similar-looking feminine endings can be confusing, as discussed in why French learners confuse words.

Why the noun should come first

English speakers often think of the adjective first because English puts adjectives before nouns. In French, many common adjectives also come before the noun, but the gender and number belong to the noun. Make a small mental pause: identify le or la, un or une, les or des before picking the adjective form. When you learn vocabulary, record nouns with their articles: la maison, un problème, des amis. Then the adjective naturally follows the same gender. That article-first habit is part of building a richer vocabulary, as described in how to build a richer French vocabulary.

A memory trick: treat article, noun, and adjective as a block

Instead of memorizing adjectives in isolation, learn short blocks: un petit garçon, une petite fille, des petits garçons. The rhythm of un petit versus une petite helps you hear the feminine. For irregular adjectives, learn the feminine block too: un beau jardin, une belle maison. When you review, say the whole phrase aloud rather than a single word. This gives your ear a pattern to compare against when you speak.

Short practice: spot the error

Read each sentence, find the agreement mistake, then check the correction below.

1. Elle est très content. → Elle est très contente.
2. J’ai vu une nouveau voiture. → J’ai vu une nouvelle voiture.
3. Ce sont des hommes très heureux. This one is correct; heureux stays the same in the masculine plural.
4. Mes amies sont intelligent. → Mes amies sont intelligentes.
5. Un plat chinois et une soupe chinois. → Un plat chinois et une soupe chinoise. (Adjectives of nationality also agree.)

If you caught at least four, your agreement instinct is forming. For more on similar-looking adjectives, see French words easy to confuse.