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Devoir vs Falloir

Verbs expressing obligation and necessity


The French verbs devoir and falloir can be confusing because they both express obligation and necessity, but in different ways. In addition, each verb has a different meaning when followed by a noun.

Devoir - When followed by an infinitive, devoir expresses obligation, probability, or supposition.

   Je dois partir
   I have to, I must, I'm supposed to leave

   Je devais étudier
   I had to, was supposed to study

   Je devrai travailler
   I will have to work

   Je devrais lire
   I would have to, I should read

   J'ai dû manger
   I had to eat, I must have eaten

   J'aurais dû manger
   I should have eaten

When followed by a noun, devoir means "to owe."

   Je dois 5 dollars
   I owe 5 dollars

   Je ne lui devais rien
   I didn't owe him anything

Conjugations of devoir

All about devoir - meaning changes in different tenses and moods

Falloir is stronger and somewhat more formal than devoir; it expresses necessity. Falloir can be used with an infinitive or the subjunctive. Because it's an impersonal verb, falloir does not conjugate for different subjects, so in order to specify the person who needs to do something, you can either use the subjunctive or an indirect object pronoun with the infinitive.

   Il faut travailler
   It is necessary to work, One needs to work.

   Il me faut travailler, Il faut que je travaille
   I need to work.

   Il ne faut pas manger
   One must not eat.

   Il nous fallait manger
   We had to eat.

   Il ne nous faut pas manger, Il ne faut pas que nous mangions
   We don't need to eat, We mustn't eat

When used with a noun, falloir means "to need."

   Qu'est-ce qu'il te faut ?
   What do you need?

   Il me faut un stylo.
   I need a pen.

Conjugations of falloir

Also see All about falloir

Summary DevoirFalloir
Type of verb personal impersonal
Register normal formal/normal
Meaning when followed by...
     infinitive must, to have toto be necessary/need to
subjunctive - - -to be necessary/need to
nounto owe to need
See the French grammar glossary if you don't understand any of these terms.
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