Must and Have to‏

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How are you today? I hope you're having a great Monday!

Today we are going to look at two verbs used in English to indicate obligation. Often people get confused with the modal verb "must" and the verb "to have to" and are unsure how to use them correctly. I will show you how. 
Hoy vamos a estudiar dos verbos usados en inglés para expresar obligación. La gente se confunde a menudo con el verbo modal "must" y el verbo "to have to" y no están seguros de cómo usarlos correctamente. Hoy te lo enseñaré.

Both "must" and "to have to" express obligation, often strong obligation depending on the tone of the speaker or the situation. However, there is a slight difference in the way they are used. 
Tanto "must" como "to have to" expresan obligación, y muchas veces una fuerte obligación según el tono del locutor. Sin embargo, hay una diferencia sutil entre sus usos.

"must" often shows that the obligation is not external or is not a rule or law. It is expressed by the speaker and is often the speaker's opinion. For example,
"must" suele mostrar que la obligación no es externa o que no es ni una regla ni una ley. Se expresa por el locutor y suele ser su opinión. Por ejemplo,

• You must be on time tomorrow or you will be in trouble.
• Debes ser puntual mañana o te echarán una bronca.

• I must call my mother tonight.
• Debo llamar a mi madre esta noche.

• You must come to my new house as it has been ages since you last visited us.
• Debes venir a mi nueva casa porque hace un montón que no nos visitas.

"must" often indicates stronger obligation than "to have to".

"to have to" shows us that the obligation comes from something or someone else. Normally it is a law or rule. For example:
"to have to" indica que la obligación viene de otra persona o de otra entidad. Suele ser una ley o una regla. Por ejemplo:

• In class you have to switch off your phones.
• En clase tenéis que apagar vuestros teléfonos.

• I have to hand in my assignment tomorrow; it's the last day. 
• Tengo que entregar mi redacción mañana; es el último día.

• John has to work every day just like the rest of us. 
• John tiene que trabajar cada día, igual que los demás.

They take on totally different meanings, however, when used in the negative. 

"must not" (or its contracted form "mustn't") expresses prohibition.

• You mustn't hit your sister. 
• No debes pegar a tu hermana.

• They mustn't talk in the exam or they will be punished.
• No deben hablar durante el examen o se les castigará.

do not have to (or its contracted form don't have to) or does not have to (or its contracted form doesn't have to) are used to state that there is NO obligation to do something or that something is not necessary.

• We don't have to go to school on Saturday.
• No tenemos que ir al colegio el sábado.

• The students don't have to study any more as the exams are all finished.
• Los estudiantes ya no tienen que estudiar porque ya se han acabado los exámenes.

• He doesn't have to sign the documents if he doesn't want to.
• No tiene que firmar los documentos si no quiere.

I hope this has been informative for you. For more on "must" and "to have to", please refer to our online courses.

Have a great week!

Bye!