Languages › French The Difference Between 'Devoir' and 'Falloir' Share Flipboard Email Print John Harper / Getty Images French Grammar Pronunciation & Conversation Vocabulary Resources For Teachers By ThoughtCo Updated February 21, 2020 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. Both devoir and falloir are extremely irregular verbs, and both are very common, perhaps the third person singular of falloir—il faut—most of all. The conjugation of both should be memorized because the French speaker is sure to need them on a daily basis. 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; I 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. Falloir 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; we need to work. Il me faut travailler; Il faut que je travaille. I need to work. Il ne faut pas manger. We mustn't 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. Summary Devoir Falloir Type of verb personal impersonal Register normal formal/normal Meaning when followed by... infinitive must have to to be necessary/need to subjunctive - - - to be necessary/need to noun to owe to need How to Conjugate the French Verb Devoir All About the French Verb Falloir French Infinitive: 'L'infinitif' Learn Some Practical French Phrases for Use in Everyday Life How to Conjugate the Irregular French Verb "Croire" Using French Semi-Auxiliary Verbs Falloir - to be necessary How to Conjugate the French Verb 'Savoir' ('to Know') How to Translate Modal Verbs into French All About the French Verb "Penser" ("to Think") How to Use the French Verb Vivre (to Live) All About the French Verb Tenir Informal French Negation: 'Pas' Without 'Ne' How to Use the French Verb 'Faillir' Basics of French Word Order with Inversion Conjugating the French Verb "Manger" "to Eat"