I sometimes see things such as Il parle vite, when I would have thought it ought to be Il parle vitement. Are these interchangeable, or is the former technically wrong but casually permissible, or…?

What about in general?

Il parle lente vs Il parle lentement?

Or others…

  • 5
    In that sentence, vite is an adverb, not an adjective. The word vitement doesn't exist (anymore) in French. As for the use of vite as an adjective, it's really not common anymore, and has mostly been replaced by rapide. Aug 26, 2013 at 7:52
  • Oooh, golden tips right there. Pro stuff. By the way, why do you live in Spain but mostly answer questions on FLU? Aug 26, 2013 at 8:00
  • As for the general rule, I would say it's just a matter of "what sounds best". You would say Il parle rapidement but not Il parle rapide, and Il parle fort but not Il parle fortement. I fear it's just a matter of usage :( Aug 26, 2013 at 8:03
  • @AlexisPigeon Dans « il parle fort », fort est un adverbe (qui se trouve être identique à l'adjectif dont il est dérivé, comme vite). Aug 26, 2013 at 8:20
  • @Aerovistae Why the question, is such a thing prohibited? :) Aug 26, 2013 at 8:50

2 Answers 2


No. When grammar calls for an adverb, you need to use an adverb. You can't use an adjective, even in colloquial French.

Il parle lentement.
* Il parle lent.

Vite looks different because it's one of the few adverbs in French that don't have the suffix -ment. It is in the company of many common adverbs: bien, mal, beaucoup, peu, très, toujours, jamais, ... Adding this suffix (with the proper inflection) to an adjective is the only productive rule to make new adverbs.

Note that vite is not an adjective in modern French (except in Québec).

A way to choose between adjectives and adverbs is to remember that an adjective qualifies a noun and agrees with it, whereas an adverb qualifies anything but a noun (verb, adjective, adverb) and is invariant (except for tous).

There is one exception which is sometimes classified as “variable adverbs”, although it could equally be classified as “adjectives qualifying adjectives”.

des fleurs fraîches cueillies = des fleurs fraîchement cueillies
des portes grandes ouvertes

Apart from a few frozen idioms like “porte grande ouverte”, this is not in common use and the real adverbial form is preferred (at least in France): “fleurs fraîchement cueillies”.

  • 1
    The breadth and depth of your knowledge on the subject of French never cease to astound me. Aug 26, 2013 at 9:35
  • I am french and I am learning things with this answer. Aug 26, 2013 at 11:35
  • I like "Il parle lent". I'm going to start speaking like that. Will definitely give me a certain style ;-)
    – Frank
    Jan 15, 2017 at 2:27
  • (don't do like me, it is NOT correct!)
    – Frank
    Jan 15, 2017 at 2:28

Le français classique n'a fait que progressivement la distinction entre adjectif et adverbe ; par exemple "coûter bon" signifiait "beaucoup" - on dit encore familièrement "coûter gros". Il ne faut donc pas s'étonner de voir chez les grands auteurs ce qui serait proscrit aujourd'hui (sans raison véritable : l'anglais est très libéral à ce sujet, sans que cela lui nuise).

  • Est-ce qu'on peut avoir des références et des dates ? Coûter bon et coûter gros n'étaient-ils pas des cas particuliers comme, par exemple, des contractions d'expressions originellement plus longues ? Oct 1, 2013 at 20:37

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