devoir (obligation / probabilité)

Devoir: Obligation or Probability

Level 2

Devoir is a versatile verb used to express obligation (must/have to), probability (must be), or intentions (supposed to). It is followed directly by an infinitive.

How It Works

The verb devoir is a versatile tool to express necessity, probability, and debt.

1. Obligation vs. Probability
In the present tense, it can mean 'must' (Je dois partir) or 'must be' (Il doit être midi). Context tells you if it's a rule or a guess.

2. To Owe (Money or Thanks)
When followed by a direct object (a noun) instead of an infinitive, devoir means 'to owe'.
Example: Je te dois dix euros. (I owe you ten euros.)

3. Advice and Regret
Use the conditionnel présent to say 'should' (Tu devrais dormir). To express regret about the past ('should have'), use the conditionnel passé (J'aurais dû étudier).

4. Past Tense Nuances

  • Passé Composé (J'ai dû): Can mean 'I had to' (and did it) OR 'I must have' (a past deduction).
  • Imparfait (Je devais): Used for habitual obligations (Je devais travailler tous les samedis) or things you were supposed to do (but perhaps didn't).

5. Spelling Note
The masculine singular past participle is dû (with a circumflex) to distinguish it from the article du. The accent is removed in the feminine (due) and plural (dus/dues).

Examples (6)

  1. Vous devez présenter votre passeport à la douane.

    You must present your passport at customs.

    Word by Word: You must to-present your passport at the customs.

    Here, 'devoir' expresses a formal obligation or legal requirement.

  2. Elle n'est pas là ; elle doit être en retard.

    She isn't here; she must be late.

    Word by Word: She not is not there; she must to-be in delay.

    In this context, 'devoir' expresses a logical probability based on the situation.

  3. Tu devrais essayer cette robe, elle te va bien.

    You should try this dress; it suits you.

    Word by Word: You should to-try this dress, it to-you goes well.

    Using the conditional 'devrais' turns the obligation into a friendly suggestion (should).

  4. Je lui dois vingt euros pour le déjeuner.

    I owe him twenty euros for lunch.

    Word by Word: I to-him owe twenty euros for the lunch.

    When followed by a noun instead of a verb, 'devoir' means 'to owe'.

  5. J'aurais dû t'appeler plus tôt.

    I should have called you earlier.

    Word by Word: I would-have had-to you to-call more early.

    The past conditional 'aurais dû' is used to express regret or things that should have happened.

  6. Il a dû oublier ses clés à la maison.

    He must have forgotten his keys at home.

    Word by Word: He has had-to to-forget his keys at the house.

    In the passé composé, 'devoir' can express a strong deduction about a past event (must have).

Common Mistakes

  • Adding a preposition like 'de' or 'à' before the following infinitive.

    Je dois de partir.
    Je dois partir.

    'Devoir' is a semi-auxiliary verb and must be followed directly by the infinitive without any preposition.

  • Using the present tense for suggestions, which can sound too aggressive.

    Tu dois te reposer.
    Tu devrais te reposer.

    While 'Tu dois' (You must) is grammatically correct, it sounds like a command. Use the conditional 'Tu devrais' (You should) for polite advice.

  • Using 'ne dois pas' to mean 'don't have to'.

    Tu ne dois pas payer.
    Tu n'as pas à payer.

    In French, 'ne dois pas' means 'must not' (prohibition). To say 'don't have to' (lack of necessity), use 'n'avoir pas à' or 'ne pas être obligé de'.

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devoir (obligation / probabilité)Level 2Devoir: Obligation or Probability

Learn This First

Understanding 'devoir' as a modal verb for obligation and probability requires knowledge of its irregular conjugation, its use in the conditional mood for nuanced meanings like 'should', and the syntactic structure of following it with a bare infinitive.

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devoir