Summary Chapter 16 (§111-12)

Devoir : irregular verb of obligation

1. Conjugation:

present : je dois, tu dois, il/elle doit; nous devons, vous devez, ils/elles doivent

passé simple: je dus, tu dus, il/elle dut; nous dûmes, vous dûtes, ils/elles durent

future/conditional stem: devr-

past participle: dû

present participle: devant

2. Meaning/use: Devoir has a number of apparently different meanings clustered around the idea of obligation. 

'must': this verb is most commonly used as a modal (like pouvoir 'can' or vouloir 'want') followed by an infinitive: Je dois partir. Elle doit étudier.

'should': in a similar sense, used in the conditional: Nous devrions attendre. ('We should wait.')

'had to/must have/was supposed to'': in past tenses, devoir expresses pressing obligations: J'ai dû préparer les déjeuners des infants ('I had to prepare the children's lunch.'); logical conclusions (the obligations of logic?): Il a dû être très surpris ('He must have been very surprised.'); an unresolved or apparent obligation: Il devait partir très tôt ('He was supposed to leave very early' -- but did he?). To distinguish between these meanings, on doit regarder le contexte ('you have to look at the context.').

'to owe': followed by a noun, the obligation is material or monetary: Il doit 50$ à ses parents.