Deber vs Deber de

Question

As usually I copy for you the last post on my website. I hope you find it useful. If you want to write some sentences to practice I will be pleased to correct them.

¡Buen día a todos!

DEBER + INFINITIVE:

When the verb “deber” is followed by an infinitive verb, expresses obligation. It’s similar to “must, should or ought”.

No debes tomar esas pastillas. You must not take those pills. ¿Qué debo hacer? What should I do?

However, it’s also admitted to express probability by RAE.

¿Cuántos años tiene tu amiga? No estoy segura. Debe (de) tener 23 o 24. How old is your friend? I´m not sure. She must be 23 or 24 years old.

When “deber” is used to express obligation, the conditional tense is usually used instead of the present tense when you want to sound more polite.

No deberías abrir la ventana si estás resfriado. You shouldn´t open the window if you are cold. Deberías gastar menos dinero hasta que encuentres otro trabajo. You should spend less money until you find another job.

DEBER DE + INFINITIVE:

When the verb “deber” is followed by the preposition “DE” and an infinitive verb, expresses likelihood. It´s similar to “must” when “must” is not used for obligation.

¿Dónde está Luis? Son las 5 de la tarde, debe de estar en casa. Where is Luis? It´s 5pm, he must be at home. ¿Por qué no está aquí? No lo sé, debe de estar ocupado. Why is not he here? I don´t know, he must be busy.

*Note: it is possible you hear “deber de” to express obligation but remember: it is not correct. Don´t learn the same native speakers´mistakes

Gracias - ian-hill, Mar 5, 2015

Another informative post. Thanks. - rac1, Mar 5, 2015

I needed that thanks. - ray76, Mar 6, 2015

I hope that you do not mind , I edited a few minor typos for you . - ray76, Mar 6, 2015

Good post! In my classes I have to deal with "native speaker mistakes" like this. I'm going to print out the article for my class. I use the "future of probablity" for "must" however. - Daniela2041, Mar 6, 2015

Nice work :) - Kiwi-Girl, Mar 7, 2015

Gracias. - annierats, Mar 7, 2015

Answer 1

I´m very happy you like so much this post

Would you have time to correct if we put up a practice sentence? - annierats, Mar 7, 2015

Sure, if not today, I can do it tomorrow ;) - SpanishSkypeorg, Mar 7, 2015

Answer 2

No debo estar aquí, escribiendo, debería cargar el coche para el viaje.

I ought not be here, writing, I should be loading up the car for the journey.

¡Perfecto! ¡Buen trabajo! - SpanishSkypeorg, Mar 7, 2015

Gracias. - annierats, Mar 7, 2015

Answer 3

Nice post. In a nutshell I would say that to be gramatically correct it should be deber for obligation and deber de for assumptions but as you mention even some of the 'best' writers of today are now using deber for assumptions as well.

Perhaps we could say that as far as modern day use goes deber is always ok but deber de should definitely be reserved for assumptions.

Answer 4

nice post

Answer 5

Worth another go it is a great teaching post.

Answer 6

Great post, and so clearly explained. I like how you linked "debre de" to the English "must". It makes it a lot easier to remember the construction! ¡Gracias!