French expresses obligation through several common structures. The most frequent tools are devoir, falloir, être obligé de, and impersonal expressions built with être nécessaire de or similar forms. Each conveys the idea that an action is required, but they differ in whether the subject is personal, impersonal, or formal.

Devoir

Devoir is the most common verb for personal obligation. It is followed by an infinitive.

Meaning

It expresses that a specific person must or has to do something.

Usage examples

• Je dois partir tôt.
  I have to leave early.
• Tu dois finir ce travail.
  You must finish this work.
• Il doit venir demain.
  He has to come tomorrow.
• Nous devons respecter les règles.
  We must follow the rules.
• Elle devait appeler sa mère.
  She had to call her mother.
• Vous devrez attendre.
  You will have to wait.
• Ils auraient dû prévenir.
  They should have warned.

Falloir

Falloir expresses necessity as an impersonal idea. It is used mainly as il faut + infinitive, or il faut que + subjunctive.

Il faut + infinitive

This construction expresses general obligation, not tied to a personal subject unless the context makes it clear.

• Il faut travailler pour réussir.
  One must work to succeed. (It is necessary to work to succeed)
• Il faut partir maintenant.
  We have to leave now. (It is necessary to leave now)
• Il faut attendre un peu.
  You have to wait a little. (It is necessary to wait a bit)

Il faut que + subjunctive

This adds a personal subject and indicates that someone must do something.

• Il faut que je parte.
  I have to leave.
• Il faut que tu viennes.
  You must come.
• Il faut qu’il écoute.
  He must listen.
• Il faut que nous finissions.
  We must finish.
• Il faut que vous soyez prudents.
  You have to be careful.

Être obligé de

Être obligé de emphasises compulsion, sometimes stronger or more formal than devoir. It is followed by an infinitive.

• Je suis obligé de partir.
  I am obliged to leave.
• Elle est obligée de travailler ce week-end.
  She is obliged to work this weekend.
• Nous sommes obligés de respecter cette règle.
  We are obliged to follow this rule.
• Ils étaient obligés de signer le document.
  They were obliged to sign the document.

This structure can carry a sense of external pressure.

Être forcé de / être tenu de

These expressions indicate constraint or duty, often legal or administrative.

• Il est forcé de quitter les lieux.
  He is forced to leave the premises.
• Nous sommes tenus de déclarer ce revenu.
  We are required to declare this income.
• Elle est tenue de fournir une preuve.
  She is required to provide proof.

Être nécessaire de / être indispensable de

These impersonal structures express that something is necessary. The subject is always il (impersonal).

• Il est nécessaire de vérifier les données.
  It is necessary to check the data.
• Il est nécessaire de changer de méthode.
  It is necessary to change method.
• Il est indispensable de rester calme.
  It is essential to stay calm.

These can also take que + subjunctive.

• Il est nécessaire que tu viennes.
  It is necessary that you come.
• Il est indispensable que nous parlions.
  It is essential that we speak.

Avoir besoin de

While not a strict obligation verb, it expresses necessity in many contexts.

• J’ai besoin de partir.
  I need to leave.
• Tu as besoin de te reposer.
  You need to rest.
• Ils ont besoin de comprendre la situation.
  They need to understand the situation.

Devoir in probability sense (distinguish from obligation)

Devoir can also express probability. Context separates this meaning from obligation.

• Il doit être chez lui.
  He must be at home. (probability)
• Il doit partir maintenant.
  He must leave now. (obligation)

The infinitive usually signals obligation, while être + adjective or noun often signals probability.

Ways to soften or adjust the obligation

Several modifiers adjust the strength of obligation.

• Je dois absolument partir.
  I absolutely must leave.
• Je dois peut-être partir.
  I might have to leave.
• Il faut vraiment que tu viennes.
  You really have to come.
• Il faut peut-être attendre.
  We might need to wait.

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Summary

• French expresses obligation mainly with devoir and falloir.
• Devoir expresses personal obligation.
• Il faut expresses general necessity, while il faut que introduces a personal subject.
• Être obligé de, être forcé de, and être tenu de add formality or external compulsion.
• Impersonal structures such as il est nécessaire de present obligation as a general requirement.
• Context distinguishes obligation from other meanings, especially with devoir.