"Deber" or "deber de"
There are two big meanings for this verb (without the "de"): obligation and to owe something/have a debt.
Deber means to have an obligation
Debemos prestar atención en clase - We must pay attention in class.
Debes entregar los papeles a tiempo - You must deliver the papers on time.
The translation here is "must" because we're using present tense.
But see what happens when we change tenses:
Ella debía contarnos todo - She had to tell us everything.
Deberéis avisar si vais - you guys will have to tell if you go.
Past tenses or future tenses would be translated with had to/ has had to, will have to, is going to have to... basically, "to have to do something".
- Deberías tomar un descanso - You should take a break.
With conditional we use "should" to translate it.
Deber also means to owe something
Me debes mil euros - you awe me a thousand euros.
Ellos te deben un favor - They owe them a favour.
With de after, there's only one meaning: a supposition, an assumption, a guess.
Pareces cansada, debes de dormir mal - you seem tired, you must sleep badly.
Deben de haber perdido el partido, están muy decepcionados - they must have lost the match, they're very dissapointed.
Debe de ser difícil ver a tu ex con ella - It must be difficult to see your ex with her.
Choose between the following words to fill in the gaps below:
Debo, deben de, deberías, debe de, debíamos, deberás, debisteis.
Creo que _______ contactar a los padres antes. - I think you had to contact the parents earlier.
Queríamos coger el día libre pero _______ ayudar en la empresa familiar. - We wanted to take the day off but we had to help in the family business.
Después de la boda _______ estar cansados. - After the wedding they must be tired.
Sé que ________ tener paciencia. - I know I must have patience.
Ellos piensan que _________ ir a un especialista. - They think you will have to go to a specialist.
Mario ha conseguido un ascenso, _______ estar orgulloso. - Mario has gotten a promotion, he must be proud.
___________ probar a meditar antes de descartarlo- You should try meditation before discarding it.
debisteis, debíamos, deben de, debo, deberás, debe de, deberías
Espero que haya sido útil! / hope it has been helpful!
¡Hasta la próxima! :)