French Adverb Formation

e.g. He runs (verb) quickly (adverb)

Adding -ment to the feminine forms (French Adverb Formation is mainly done like this)

Example
Égal > feminine: égale (equal)
Adverb: également equally

-ment is added to the masculine form, only if the masculine form of the adjective ends with a vowel

Vrai real
Vraiment really
Forcé forced
Forcément necessarily

Adjectives ending in -ant and –ent (same pronunciation) form adverbs ending with -amment and –emment

Constant constant
Constamment constantly
Récent recent
Récemment recently

Exceptions

Lent slow
Lentement slowly
Présent present
Présentement presently

Some adverbs in French Adverb Formation follow the same pattern as the adjective forcément, even if the ending doesn’t correspond

Aveugle blind
Aveuglèment blindly
Commun common
Communément communally
Confus confuse
Confusément confusedly
Enorme enormous
Enormément enormously
Exprès express
Expressément expressly
Impuni unpunished
Impunément with impunity
Intense intense
Intensément intensively
Précis precise
Précisément precisely
Profond deep
profondément deeply

The French Adverb Formation of the following adverbs based on their adjectives but, they are completely irregular

Bon good
Bien well
Bref brief
Brièvement briefly
Continu continuous
Continuellement continuously
Gai cheerful
Gaiement cheerfully
Gentil kind
Gentiment kindly
Mauvais bad
Mal badly
Mieux best
Meilleur better
Moins less
Moindre lesser
Petit small
Peu few
Traître treacherous
Traîtreusement treacherously

Words like ainsi, donc, dedans are adverbs

Ainsi, tu es d’accord? = So, you are agreeing?

Some of these relate to conjunction

Dans in = dedans inside

Some are independent

Donc... then...

Some adjectives are used as adverbs in French Adverb Formation

Bas, haut = parler bas/fort speak softly/loudly
Bon, mauvais = sentir bon/mauvais smell god/bad
Cher = coûter cher, payer cher cost/pay a lot
Court = couper court cut short
Dur = travailler dur work hard
Juste, faux = chanter juste/faux sing in/out of tune
Net = refuser net refuse point blank

Used in sentences when the adjective has no corresponding adverbs

Il me regarda d’un air triste = he looked at me sadly
Oh oui, dit il d’une voix contente = “oh yes”, he said contentedly
Elle répondit d’une voix basse = she answered softly
Je l’ai fait avec soin = I did it carefully
L’équipe s’est battue avec beaucoup de courage = the team fought very courageously
Elle l’a fait sans hésitation = she did it unhesitatingly