How to say "must have [done something] with the verb deber

To express in Spanish that something must have happened, as when making an assumption or wondering what must have happened, we can use the verb deber in two different ways:

We can use deber conjugated in El Pretérito Perfecto (followed by an infinitive). For example:

Manuela ha debido llamar a la policía.
Manuela must have called the police.

Todavía no han llegado, su avión ha debido retrasarse.
They haven't arrived yet, their flight must have had a delay.

Sara ha debido de dejar a su hijo en la guardería esta mañana.
Sara must have left her son at the nursery this morning.

Cristina ha debido de ser una buena profesora, sus estudiantes le han comprado flores.
Cristina must have been a good teacher, her students bought her some flowers.

Here we are not talking about obligation, which is one of the uses of the modal verb deber, but instead are wondering/assuming what must have happened. The reason to make such an assumption is very often expressed by a fact.

For example:

"Cristina ha debido de ser una buena profesora." (assumption)

"Sus estudiantes le han comprado flores." (fact)

The same thing can be expressed using this structure with deber. Have a look at the examples again:

 

Manuela debe haber llamado a la policía.
Manuela must have called the police.

 

Todavía no han llegado, su avión debe haberse retrasado.
They haven't arrived yet, their flight must have had a delay.

 

Debe de haber llovido esta noche, porque los coches están mojados.
It must have rained tonight because the cars are wet.

As you can see from the previous examples, when we use deber with this nuance of assumption/wondering, we can optionally use the preposition "de" after deber.

When the main verb of the sentence is a pronominal verb (uses a reflexive pronoun) you can place the pronoun either in front of the main verbal structure or attached to haber. For example:

Su avión se ha debido retrasar.
His plane must have been delayed.

Su avión ha debido retrasarse.
His plane must have been delayed.

Su avión se debe haber retrasado.
His plane must have been delayed.

Su avión debe haberse retrasado.
His plane must have been delayed.

This would be incorrect:

"Su avión debe haber retrasado se.

"Su avión ha debido se retrasar.

"Su avión ha se debido retrasar.

Note that when we use the modal verb deber conjugated in:

"Ella debió aceptar el dinero."
"Ella debió haber aceptado el dinero."

the meaning is generally different. It would normally be translated as "should have done something" instead.

See also Deber versus Deber de (obligation and assumption) and Deber in El Conditional Simple + haber + participle = should have 

Learn more about these related Spanish grammar topics

Examples and resources

Manuela debe haber llamado a la policía.
Manuela must have called the police.


Cristina ha debido de ser una buena profesora, sus estudiantes le han comprado flores.
Cristina must have been a good teacher, her students bought her some flowers.


Su avión ha debido retrasarse.
His plane must have been delayed.


Manuela ha debido llamar a la policía.
Manuela must have called the police.


Todavía no han llegado, su avión ha debido retrasarse.
They haven't arrived yet, their flight must have had a delay.


Su avión se ha debido retrasar.
His plane must have been delayed.


Su avión debe haberse retrasado.
His plane must have been delayed.


Debe de haber llovido esta noche, porque los coches están mojados.
It must have rained tonight because the cars are wet.


Su avión se debe haber retrasado.
His plane must have been delayed.


Sara ha debido de dejar a su hijo en la guardería esta mañana.
Sara must have left her son at the nursery this morning.


Todavía no han llegado, su avión debe haberse retrasado.
They haven't arrived yet, their flight must have had a delay.


Su avión ha debido retrasarse.
His plane must have been delayed.


Q&A Forum 2 questions, 2 answers

AllisonC1Kwiziq Q&A regular contributor

Optional "de" in what instance?

Would you explain more clearly when one does or does not use "de" in this form? As far as I can extrapolate, if an infinitive is to follow, we use "de" but otherwise no?

Or is it optional in any instance?

Asked 10 hours ago
InmaKwiziq team memberCorrect answer

Hola Allison:

In the lesson, after the boxes containing examples, some using the preposition de and some without it, we say: "As you can see from the previous examples, when we use deber with this nuance of assumption/wondering, we can optionally use the preposition "de" after deber."

This lesson is about how to say "something must have happened"; this is talking about assumption, not obligation. So for all the examples in this lesson "de" is optional. 

To see with more detail the difference between deber and deber de, please have a look at this other lesson which explains precisely this. There is a link at the bottom of the lesson about "something must have happened". Here it it.

I hope it is useful.

Saludos

Inma

Optional "de" in what instance?

Would you explain more clearly when one does or does not use "de" in this form? As far as I can extrapolate, if an infinitive is to follow, we use "de" but otherwise no?

Or is it optional in any instance?

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AllisonC1Kwiziq Q&A regular contributor

English grammar error


They should drink quite a lot.They must have drunk quite a lot.They actually drank quite a lot.They couldn't drink a lot.

Sorry to be persnickety--"drunk" is only an adjective in English, never a verb. "Have drank" is the correct form.
Asked 10 hours ago
AlanC1Kwiziq Q&A regular contributor

I don't agree, Allison. "Drunk" is the past participle, so "have drunk" is correct. Maybe "have drank" is used in American English?

English grammar error


They should drink quite a lot.They must have drunk quite a lot.They actually drank quite a lot.They couldn't drink a lot.

Sorry to be persnickety--"drunk" is only an adjective in English, never a verb. "Have drank" is the correct form.

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