Hoy os dejamos unos “truquis” para utilizar los modales de obligación “must & have to” y también cómo expresar falta de obligación (lack of obligation) con los modales don’t have to, don’t need to, didn’t need to. Vamos allá!

HAVE TO / MUST

We use these verbs to say that is necessary to do something, but there are some differences:

Have to
The speaker is just giving facts. Or there’s an «outside authority» who tells you to do something.
E.g. I have to complete the report for our client.

We can use “have to” in all verb tenses.

Must
The speaker thinks is necessary, feels is his responsibility to do something.
E.g. I must finish all these paperwork today.

We only use “must” in the present tense, to express obligation in other tenses we use “have to”.
E.g. I had to finish all the paperwork last Friday.
I will have to finish all the paperwork before Friday.

DON’T HAVE TO / MUSTN’T

When used in the negative form, they mean different things:

Don’t have to /don’t need to
It means is NOT necessary that we do something.
E.g. You don’t have to bring anything.
They don’t need to bring anything.

Mustn’t
It means is necessary NOT to do something. (it’s an obligation not to do something).
E.g.He mustn’t talk to us like that.
You mustn’t tell anyone.
We mustn’t be late for the meeting.

DIDN’T NEED TO / DIDN’T HAVE TO DO

We use didn’t need to / didn’t have to meaning that something was not done because it was not necessary.
E.g. We didn’t need to call the technical services, we just fixed it ourselves.
They didn’t need to work until late. We still have time until deadline.
I didn’t have to prepare a cake, but they all appreciated it.

Parece mucho pero en realidad son tres cositas, te las resumimos:

-Must / have to > obligación, sobre todo “have to” que se puede utilizar en cualquier tiempo verbal

-Mustn’t > obligación de NO hacer algo (o prohibición de hacer algo)

-Don’t have to / don’t need to (y sus formas en pasado) > falta de obligación, o lo que es lo mismo, no es necesario hacer algo.

Esperamos que te sirva de ayuda 😉

La diferencia entre to y for en inglés es algo que nos suele costar bastante, porque para nosotros es confuso saber cuándo “para” es con “to” y cuándo con “for” en inglés.

Este es el error más común que cometemos al usar to y for

 We need to leave now for to arrive on time.
 We need to leave now to arrive on time.

 I’m saving money for to travel around the world.
 I’m saving money to travel around the world.

 These trainers are for to running.
 These trainers are for running.

 This money is for to buying a new car.
 This money is for buying a new car.

Normalmente o bien usamos to o bien usamos for, usar los dos juntos no es correcto. Para saber cuál es diferencia entre to y for en inglés, lo más fácil es pensar por un momento si nos referimos a la finalidad o para qué sirve algo o si queremos indicar el motivo por el que hacemos algo.

For > finalidad – para qué sirve algo

Lo más normal en este caso, es que usemos for + sustantivo o bien for + verbo en gerundio (-ing). Vamos a ver unos ejemplos de uso para cada uno.

for + noun

Doing exercise is good for your health.
I bought a suit for my new job.
This book is for dummies.
That red sofa is for our living room.

for + verb -ing

These trainers are for running.
A ladle is a big spoon used for serving soup.
This money is for buying a new car.
Traveling is great for meeting new people.
Watching tv in English is good for improving your listening skills.

To > motivo, razón – por qué hacemos algo

Es bastante frecuente que la construcción sea to + verbo. De hecho, un buen truco para saber si efectivamente tiene más sentido con to, es probar añadiendo la expresión in order to. Aunque esta expresión se usa también para hablar de finalidad, es una buena forma de probar y ver si funciona. Otra manera es sustituir o añadir because (con algunos ajustes en la frase) que es la palabra que usamos para dar una razón. Observa los siguientes ejemplos

We need to leave now (in order) to arrive on time. (because we want to arrive on time)
I’m saving money (in order) to travel around the world. (because I want to travel)
She came here (in order) to see you. (because she wants to see you)
I go to the gym (in order) to keep fit. (because I want to keep fit)

Básicamente así sabremos cuál es la diferencia entre to y for en inglés, tendremos que distinguir si nos referimos a la finalidad (para qué) o al motivo (por qué). Hay otros usos de to y for pero quizá no sean tan confusos.

Otros usos de to & for

For

I made a cake for her.
This phone call is for you.
I bought this toy for my dog.
Can you open the door for me please?
I was waiting for her at the restaurant.

We’ve lived here for 5 years. (period of time)
I have worked with them for 2 years. (period of time)
Are you for or against renewable energy? (agree with)
I was in London for a conference. (reason)
Let’s go out for a drink. (reason)

To

They went to Paris last year. (destination)
She’s going to Cambridge with her class. (destination)
What is the next train to the city centre? (destination)
I prefer series to films. (comparing)
We prefer running to swimming. (comparing)
It’s ten to seven. (telling the time)
From here to the office I must walk 20 minutes. (distance)
There’s a parking lot next to our building. (place)

Pues ya tienes el truco para saber cuál es la diferencia entre to y for en inglés. A partir de ahora antes de decir for to + verbo piensa si es mejor usar uno o otro en la frase que estás construyendo.

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