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French grammar - Must, have to - the verb devoir

Must, have to - the verb devoir

The verb devoir has several meanings related to obligation, supposition, and expectation.

It can mean 'to have to' or 'must' in the sense of 'obligation' or 'requirement'.

-- For example - obligation or requirement: 'I have to go to work.'

-- In the negative it means the imperative 'must not' and NOT the optional 'to not have to'.

It can also mean 'to be due to' or 'to be bound to' in the sense of expectation of something happening.

-- For example - expectation: 'A new shop is due to open.'

It can also mean 'must' or 'to be probable' as a supposition or guess.

-- For example - supposition: 'He must sleeping' or 'He must have fallen asleep.'

With the preposition à the verb devoir à means 'to owe' (a debt for example). It therefore should take an indirect object pronoun.

-- For example - obligation: 'I owe him some money'

There can in some instances be ambiguity about which of these meanings in intended. Context is required to clear this up.

-- Using words like absolument, tout de suite, à tout prix, impérativement, or vraiment can be used to remove ambiguity.

The past participle of devoir is irregular . Note the circumflex accent (accent circonflexe).

Examples:
Je dois manger.
I must eat.
J'ai dû manger.
I had to eat.
J'ai dû aller à l'école.
I had to go to school.
Il doit appeler sa mère.
He has to call his mother. *OR* He must be calling his mother.

There is ambiguity here

Il doit appeler sa mère tout de suite.
He must call his mother right away.

No ambiguity now

Il a dû appeler sa mère.
He had to call his mother. *OR* He must have called his mother.

There is ambiguity here

Il a dû appeler sa mère impérativement.
He had to call his mother urgently.

No ambiguity now

impérativement means 'imperatively' or 'urgently'

Il a dû le laisser là.
He had to leave it here. *OR* He must have left it there here.

There is ambiguity here

Il a dû le laisser là. Il a dû l'oublier.
He must have left it here. He must have forgotten it.

No ambiguity now with context

J'ai trouvé l'écharpe d'Angela. Elle a dû l'oublier.
I found Angela's scarf. She must have forgotten it.

Context makes the meaning unambiguous

Tu dois être fatigué.
You (familiar) are probably tired.

Probably unambiguous

Le train doit être en retard.
The train is probably late.

Probably unambiguous

Dois-tu étudier ce soir ?
Do you have to study tonight?
Nous devons nous dépêcher, nous sommes déjà en retard.
We have to hurry; we are already late.

se dépêcher (verb) means 'to hurry'

Ils doivent économiser de l'argent.
They have to save money.

économiser (verb) means 'to save (money)'

Elle doit être contente.
She must be (is probably) happy.
Vous devez absolument être ici à l'heure.
You absolutely must be here on time.

absolument means 'absolutely'

Nous devons le faire tout de suite.
We have to do it right away.
Nous avons dû le faire tout de suite.
We had to do it right away.
Ils doivent le finir tôt demain matin à tout prix.
They have to finish it early tomorrow morning at all costs.

à tout prix means 'at all costs' or 'at any price'

Elle doit être là à midi.
She has to be here at noon.
Elle ne doit pas être là à midi.
She must not be here a noon.

NOT 'She does not have to be here at noon'

Tu ne dois pas faire ça !
You (familiar) must not do that.
Tu ne dois jamais faire ça !
You (familiar) must never do that.
Vous ne devez pas fermer la porte à clé.
You must not lock the door.

fermer à clé (verb) means 'to lock'

La nouvelle salle de sport doit bientôt ouvrir.
The new gym is due to open soon.

devoir here 'to be due to'

Nous avons dû laisser la voiture au parking.
We had to leave the car in the carpark.
Combien dois-je à Paul ?
How much do I owe Paul?

devoir à means 'to owe (someone something)'

Combien est-ce que je lui dois ?
How much do I owe him?
Tu ne lui dois rien !
You (familiar) don't owe him∆her anything!