Verbos auxiliares se usan normalmente con un verbo principal para añadir un significado adicional a una frase. También pueden utilizarse para conjugar verbos en tiempos compuestos, para preguntar y contestar a preguntas generales o para expresar negación y la voz pasiva.
Los tres verbos auxiliares más comunes, "be", "have" y "do", se llaman auxiliares primarios.
Como los verbos ordinarios tienen tanto infinitivo como formas irregulares conjugadas. A veces pueden ser usados solos como verbos principales, por ejemplo, “He does just as I say” (to do), “I had everything I needed” (to have), “We have never been to England” (to be).
Como auxiliar “be” se utiliza principalmente para formas continuas, por ejemplo “I am learning English” (to learn) y para la voz pasiva, por ejemplo, “She was raised by her mother” (to raise).
“Have” se usa también como auxiliar para formar tiempos compuestos como presente o pasado perfecto, tanto en voz activa como pasiva. Por ejemplo, “Have you tried to call him?” (to try), “He had been given a second chance” (to give).
“Do” se utiliza como el verbo auxiliar para formar preguntas y oraciones negativas con verbos ordinarios. En la forma negativa hablada, “not” se contrae y cambia a “-n’t”, por ejemplo, “Did you see that? – No, I did not / didn’t!” (to see). “Do” también puede utilizarse para acentuar los verbos ordinarios, por ejemplo, “Stop calling me lazy, I did clean the bathroom!” (to clean)
Los verbos modales son un tipo especial de los verbos auxiliares. Siempre se utilizan con el infinitivo del verbo principal sin “to”, por ejemplo, “You can leave now” (to leave), “She might know about this already” (to know).
Tienen sólo una forma y no se conjugan con otros auxiliares (no hay tiempos continuos o formas pasivas): no se puede decir “she musts”, “I am mighting” o “you were coulded”. Los negativos se forman añadiendo "not" después del verbo modal. Algunos verbos modales pueden ser contratados: “can’t”, “couldn’t”, “wouldn’t”, “shouldn’t”, “won’t” y “shan’t”.
Dos verbos modales pueden utilizarse como formas pasadas de otros: can (presente) could (pasado) and will (presente, futuro) would (pasado).
Énfasis
do/does/did
Actually I do know that, but thanks!
Habilidad
can
be able to/am able to/are able to/is able to/was able to/were able to
could
I can read pretty fast.
She was not able to catch her plane.
Could you finish the test yesterday?
Permiso
may
might
Can I leave now?
May I come in?
Could you close the window?
Might I join you?
Prohibición
cannot/can't
must not/mustn't
may not
be not to
You can't walk on the grass.
He must not fight with his sister.
You may not smoke in this room.
We are not to travel alone.
Obligación / Orden
must
have to/have got to
be to
will
shall
We must stay quiet.
You have to go now.
I am to stay here and wait for her.
You will stop answering back now!
You shall work harder next time.
Deber / Consejo
should
ought to
He should study more seriously.
You ought go to bed earlier.
You must see this movie once in your life!
Necesidad
have to/has to/had to
need to/needs to/needed to
He must stop complaining constantly.
I have to catch my train at 8 am.
I need to pay the rent every month.
Ausencia de necesidad
do not have to/don't have to/does not have to/doesn't have to/did not have to/didn't have to
need not/needn't/needs not/do not need to/don't need to/does not need to/doesn't need to/did not need to/didn't need to/needed not
You don't have to come if you don't want to.
You needn't worry, he will be fine.
Compromiso
will/'ll
shall/'ll
I'll never lie to her again.
I shall honour this promise.
Solicitud / Invitación
would
Shall we dance?
Will you come to the party tonight?
Would you please help me?
Imposibilidad
could not/couldn't
will not/won't
would not/wouldn't
This can't be right.
He couldn't stop crying when he heard the news.
Regrets won't help you now!
I told you it just wouldn't work.
Certeza
That'll be him ringing the doorbell.
Probabilidad
She should be home by now.
They must be very proud.
He can't be more than thirty.
Posibilidad
He could be dead already.
It may or may not rain for the picnic.
This might be the answer to my problem.
It can be that she didn't want to bother you.
Hábito
used to
I used to play in this park when I was little.
For years, she would visit her friends every Sunday.
Desafío
dare
do not dare/don't dare/does not dare/doesn't dare/daren't
did not dare/didn't dare/dared not
How dare you call me selfish?
I don't dare look down from the top.
She dared not complain about her bully.
