Most French adverbs are built from an adjective, in much the same way that English adds “-ly” to turn “slow” into “slowly”. The usual method is to take the feminine form of the adjective and add -ment. A smaller group of adjectives follow their own patterns, and a handful of common adverbs do not come from an adjective at all.

The basic rule: feminine form plus -ment

For most adjectives, start with the feminine singular form and add -ment to the end. Forming the feminine is not always as simple as adding an -e, though. It follows several different patterns, depending on how the masculine form ends.

Adjectives that simply add -e

• Certain, certaine, certainement – “certainly”
• Correct, correcte, correctement – “correctly”
• Exact, exacte, exactement – “exactly”
• Général, générale, généralement – “generally”
• Grand, grande, grandement – “greatly”
• Lent, lente, lentement – “slowly”
• Normal, normale, normalement – “normally”
• Parfait, parfaite, parfaitement – “perfectly”
• Seul, seule, seulement – “only”
• Spécial, spéciale, spécialement – “specially”

Adjectives ending in -eux, which change to -euse

• Dangereux, dangereuse, dangereusement – “dangerously”
• Généreux, généreuse, généreusement – “generously”
• Heureux, heureuse, heureusement – “fortunately”
• Nerveux, nerveuse, nerveusement – “nervously”

Adjectives ending in -el, which double the l before -e

• Naturel, naturelle, naturellement – “naturally”
• Personnel, personnelle, personnellement – “personally”
• Réel, réelle, réellement – “really”

Adjectives ending in -er, which change to -ère

• Léger, légère, légèrement – “lightly”
• Premier, première, premièrement – “firstly”

Other irregular feminine forms

• Complet, complète, complètement – “completely”
• Doux, douce, doucement – “softly”
• Franc, franche, franchement – “frankly”

For example:

• Le train avance lentement. – “The train moves slowly.”
• Elle répond franchement à la question. – “She answers the question frankly.”

Adjectives already ending in a vowel

When the masculine form of the adjective already ends in a vowel, the feminine form is not needed. -Ment is simply added to the masculine form.

• Absolu, absolument – “absolutely”
• Aisé, aisément – “easily”
• Joli, joliment – “nicely”
• Modéré, modérément – “moderately”
• Poli, poliment – “politely”
• Résolu, résolument – “resolutely”
• Vrai, vraiment – “truly”

For example:

• C’est vraiment intéressant. – “It’s truly interesting.”
• Elle a répondu poliment. – “She answered politely.”

Adjectives ending in -ent or -ant

Adjectives ending in -ent form their adverb with -emment, and adjectives ending in -ant form their adverb with -amment. Both endings are pronounced the same way, roughly like “amm”.

• Brillant → brillamment – “brilliantly”
• Bruyant → bruyamment – “noisily”
• Constant → constamment – “constantly”
• Courant → couramment – “fluently”
• Évident → évidemment – “obviously”
• Fréquent → fréquemment – “frequently”
• Intelligent → intelligemment – “intelligently”
• Méchant → méchamment – “nastily”
• Patient → patiemment – “patiently”
• Prudent → prudemment – “carefully”
• Récent → récemment – “recently”
• Savant → savamment – “knowledgeably”
• Suffisant → suffisamment – “sufficiently”

For example:

• Il a déménagé récemment. – “He moved recently.”
• Elle parle couramment espagnol. – “She speaks Spanish fluently.”

Adverbs that do not come from -ment

A small number of common adverbs are irregular, either because they take a different form to the pattern above or because they do not come from an adjective at all.

• Bon → bien – “good → well”
• Bref → brièvement – “brief → briefly”
• Gentil → gentiment – “kind → kindly”
• Mauvais → mal – “bad → badly”
• Meilleur → mieux – “better → better”
• Petit → peu – “small → not much”

When there is no adverb form

Some adjectives have no natural adverb, or one that would sound awkward. French then uses a phrase instead, usually d’une façon or d’une manière followed by the adjective, or avec followed by a related noun.

• Il a réagi d’une façon étrange. – “He reacted in a strange way.”
• Elle a parlé avec calme. – “She spoke calmly.”

Summary

Most French adverbs are formed by adding -ment to the feminine form of an adjective, as in lente to lentement. Forming that feminine form follows several patterns of its own: some adjectives simply add -e, others change -eux to -euse, double a final -l, change -er to -ère, or shift in some other irregular way, as with doux and franc. Adjectives already ending in a vowel skip the feminine step and add -ment straight to the masculine form. Adjectives ending in -ent or -ant form their adverb with -emment or -amment instead. A few common adverbs, such as bien and mal, are irregular and do not follow any of these patterns, and where no adverb exists at all, French falls back on a phrase such as d’une façon or d’une manière plus the adjective.