1. Tener que + infinitive is one way to express obligation or necessity. This expression is similar to the English “to have to…”. Tener is conjugated according to the subject of the sentence.
Tengo que ir al médico (I have to go to the doctor).
Carlota tiene que escribir un informe (Carlota has to write a report).
Marisa y Ramón tienen que comprar una lavadora (Marisa and Ramón have to buy a washing machine).
2. Hay que + infinitive is used to express the idea of “something has to be done” or, “it is necessary to do something.” It is a more general expression and since there is no subject, the verb form “hay” is always used.
Hay que tener pasaporte para viajar a EEUU (It is necessary to have a passport to travel to USA).
Hay que estudiar mucho para aprender un idioma (One must study a lot to learn a foreign language).
3. Deber + infinitive, when used in this way, deber is frequently similar in meaning to the English “must,” or “ought”:
Debemos estudiar el vocabulario (we ought to study vocabulary).
¿Qué bicicleta crees que debo comprarme? (Which bike do you think I must buy?).
The use of deber to express obligation can be made more polite by using the conditional tense instead of the present tense. In this case, could be translated like “should” (check here the whole conjugation of deber), and sounds more like an advice:
Deberías ir al médico (you should go to the doctor).
Deberíamos comprar un coche nuevo (we should buy a new car).
Now you can practice with a quiz. Click on the link if you want to learn more about verb TENER and HAY (from haber). Remember you can get in touch with your tutor with any question you have. Don’t you have a Spanish personal tutor yet?