Devoir: Obligation, Probability, Owing

Devoir is the heaviest-working modal in French. A single verb covers what English splits across must, have to, should, ought to, be supposed to, owe, and the speculative must be / must have. The reading depends on tense, person, context, and sometimes intonation — il doit étudier could mean "he has to study" (obligation), "he must be studying" (inference about right now), or "he is supposed to study" (schedule). French speakers disambiguate effortlessly; learners need a few weeks of exposure before the readings click.

This page drills the full irregular paradigm — including the famous past participle dû with its disambiguating circumflex — and walks through each of the four main readings: obligation, probability/inference, schedule/expectation, and the transitive owe meaning. It also covers the conditionnel devrais (should) and the conditionnel passé aurais dû (should have), which are arguably the highest-payoff conditional forms in French. By the end you should be able to choose the right tense of devoir deliberately, and recognize which reading a French speaker intends when they use it.

Full conjugation

Devoir belongs to the family of recevoir, apercevoir, concevoir — verbs ending in -evoir that share a stem-vowel alternation pattern.

Indicatif

Conditionnel and subjonctif

Participes

• Participe passé: dû (masculine singular, with circumflex), due (feminine singular), dus (masculine plural), dues (feminine plural)
• Participe présent: devant

Notes on the paradigm

Three things to memorize:

1. The strong/weak/distinct stem alternation in the present: strong doi- in je dois, tu dois, il doit; weak dev- in nous devons, vous devez; and a distinct doiv- in ils doivent. Same three-way split as pouvoir and vouloir. The pattern recurs.

2. The futur stem devr-: je devrai, tu devras, il devra, nous devrons, vous devrez, ils devront. This is the same stem that powers the conditionnel devrais. Unlike pouvoir (pourr-) and vouloir (voudr-), the devr- stem has only one r. Don't write devrr-.

3. The past participle dû with its circumflex — see the next section.

The pronunciation is /dwa/ for the doi- forms (dois, doit, doivent) and /də.vɔ̃/ /də.ve/ for devons, devez. Four of the six conditional forms — je, tu, il, ils — collapse to /də.vʁɛ/, identical in sound, distinguished only by the subject pronoun. This is why subject pronouns are obligatory.

The circumflex on dû — and only on dû

The masculine singular past participle of devoir takes a circumflex: dû. The feminine and plural forms drop it: due, dus, dues.

The circumflex exists only to disambiguate dû (past participle) from du (the contraction de + le used as a partitive article). Compare j'ai dû partir (I had to leave) with j'ai mangé du pain (I ate some bread): two completely different words that would be spelled identically without the circumflex.

This circumflex-for-disambiguation appears on exactly three masculine singular past participles in French: dû (from devoir), crû (from croître, "to grow" — distinguishing it from cru, "believed," the participle of croire), and mû (from mouvoir, "to move"). All three drop the circumflex in the feminine and plural. Memorize this as a closed set.

Reading 1: obligation — must / have to

The most basic use of devoir is to express obligation: the subject has to do something.

The force is closer to English have to than to must — je dois is a neutral statement of obligation, not a thunderous command. Compared with il faut que je parte (impersonal, urgent) or je suis obligé de partir (heavy, formal), je dois partir is the everyday default.

In the negative, je ne dois pas + infinitive carries a prohibition or strong recommendation against the action:

A subtle point: the negative obligation reading shifts depending on emphasis. Je ne dois pas partir normally means "I mustn't leave"; for "I don't have to leave" (the obligation simply doesn't apply), French speakers tend to use je ne suis pas obligé(e) de partir or je n'ai pas à partir.

Reading 2: probability / inference — must be

The same surface forms (je dois, tu dois, il doit) carry a completely different reading: probability or inference. Il doit être fatigué does not mean "he has to be tired" — it means "he must be tired" (= I infer that he is tired, based on what I see).

This inference reading typically pairs with stative verbs (être, avoir, savoir, falloir) and with present-tense states. With dynamic action verbs and a future-pointing context, the obligation reading dominates. Context disambiguates almost effortlessly for native speakers.

The inference reading also extends into the past via the passé composé:

So il a dû partir has two readings: "he had to leave" (obligation in the past) and "he must have left" (past inference). Context, again, decides.

Reading 3: scheduled / supposed to

When the subject is something governed by a schedule or expectation — a train, a meeting, a delivery — devoir in the present takes a "supposed to" reading.

The imparfait (il devait pleuvoir) is the form for "was supposed to" — particularly when the expected event did not occur. This is one of the most useful nuances of devoir's tense system, and English speakers often miss it because they default to the passé composé for past events.

Reading 4: owe (transitive)

Outside its modal use, devoir has a transitive meaning: "to owe (someone) (something)." The object is what is owed, the indirect object (with à) is the recipient.

The "owe" meaning extends metaphorically: je te dois la vie (I owe you my life), nous devons cette victoire à notre coach (we owe this victory to our coach). The pattern is devoir + nom + à + bénéficiaire.

This transitive use is technically not a modal use — there's no infinitive — but it lives in the same verb and is part of the devoir package every learner has to internalize.

Conditionnel devrais: should

The conditionnel of devoir — je devrais, tu devrais, il devrait, nous devrions, vous devriez, ils devraient — is the standard French way to say should. There is no separate French word for should; the conditionnel of devoir does the entire job.

The shift from tu dois to tu devrais is significant: tu dois te reposer is an order from a position of authority (a doctor, a parent); tu devrais te reposer is friendly advice between equals. In adult-to-adult interaction, tu devrais is almost always the right register.

The conditionnel of devoir in inference contexts means "should" in the probability sense:

For full coverage of the should form, see devrais-should.

Conditionnel passé: aurais dû = should have

For the past — "I should have, you should have" — French uses the conditionnel passé: aurais / aurait / aurions / auriez / auraient + the past participle dû + the infinitive of the lexical verb.

After dû, the lexical verb is always in the infinitive, never the past participle. J'aurais dû partir, never j'aurais dû parti. This is parallel to English: should have left is should have + infinitive leave (in English the infinitive happens to look like the past participle for leave, but in French the distinction is sharp).

This aurais dû + infinitive construction is the single most common way to express regret or reproach about the past in French. Drill it deliberately:

• J'aurais dû... = I should have ... (regret about myself)
• Tu aurais dû... = You should have ... (reproach toward another)
• On aurait dû... = We should have ... (collective regret)
• Tu n'aurais pas dû... = You shouldn't have ... (reproach for an action)

See conditionnel-passe-regret for the full triplet aurais dû / aurais pu / aurais voulu.

Devoir in the passé composé and imparfait: a sharp split

The passé composé / imparfait choice with devoir tracks the same aspectual distinction we saw with pouvoir and vouloir, but the readings are sharper:

• J'ai dû
  • infinitive
  = "I had to / I must have" — perfective. Either an obligation that I actually carried out, or a past inference.
• Je devais
  • infinitive
  = "I was supposed to / I had to (in general)" — imperfective. A past plan or a state of obligation, often unrealized or backgrounded.

A subtle pattern: je devais often carries an "and it didn't happen" implication, while j'ai dû carries an "and it did happen" implication. This is one of the cleanest demonstrations of the imparfait/passé composé contrast in the modal system.

Negation, pronouns, and questions

Negation wraps the conjugated devoir:

Object pronouns sit before the infinitive in modal use:

In transitive owe use, pronouns sit before devoir (since the object belongs to devoir itself, not to a following infinitive):

Questions form via inversion or est-ce que:

Common Mistakes

Mistake 1: Forgetting the circumflex on dû in masculine singular.

Mistake 2: Adding the circumflex on the feminine or plural forms.

Mistake 3: Using a past participle after aurais dû instead of the infinitive.

Mistake 4: Using je dois in adult-to-adult advice contexts.

Mistake 5: Confusing je devrai (futur) and je devrais (conditionnel).

Mistake 6: Reading il a dû partir as only past obligation.

Key takeaways

Devoir is the most overloaded modal in French — it covers obligation, probability, schedule, and (transitively) owing. Memorize the three present-tense stems (doi-, dev-, doiv-), the futur stem devr- with one r, and the past participle dû with its disambiguating circumflex on the masculine singular only. Feminine due, masculine plural dus, feminine plural dues all drop the circumflex.

The four readings — je dois travailler (obligation), il doit être fatigué (inference), le train doit arriver à 16h (schedule), je te dois 20 euros (owe) — are disambiguated by context, person, and tense. The conditionnel devrais is the standard "should" — French has no other word for it. The conditionnel passé aurais dû + infinitive (never past participle) is the workhorse of regret and reproach: j'aurais dû partir, tu aurais dû me prévenir. The passé composé / imparfait split is sharp: j'ai dû (had to / must have — perfective), je devais (was supposed to — imperfective, often unrealized).