This document discusses modal verbs in English. It explains that modal verbs are unchanging and do not conjugate for person or number. They are always followed by a base verb form. Modal verbs express functions like permission, ability, obligation, prohibition, advice, and probability. Examples are given for how modal verbs are used to express these different functions in both the present/future and past tenses.

1. MODAL VERBS

2. INTRODUCTION
• Los verbos modales son invariables.
•
•
•
No se conjugan. Tienen la misma
forma en todas las personas
No necesitan auxiliares para formar
negaciones y preguntas
Siempre van seguidos de un verbo
en infinitivo (you should go to...)
Expresan diferentes FUNCIONES
(permiso, habilidad, prohibición...)

3. PROBABILITY
• Present/ future
o
That story COULD/ MIGHT be true
(vaguely probable)
(esa historia podría ser verdad)
That story MAY be true (probable)
(quizá sea verdad)
o That story MUST be true (highly
probable, certain)
(debe ser verdad)
o

4. POSSIBILITY/ PROBABILITY
•
Past (se utiliza el verbo modal seguido de un infinitivo
•
El infinitivo perfecto se forma con: HAVE + PAST PARTICIPLE
perfecto)
–
That story COULD/ MIGHT have been true (vaguely
probable)
(podría haber sido verdad)
–
That story MAY have been true (probable) (quizá haya
sido verdad)
–
That story MUST have been true (highly probable, certain)
(debe haber sido verdad)

5. OBLIGATION
• Present/ future (deber, tener que)
I MUST write a card for my mother
because it's her birthday
o I HAVE TO start work at 8:30
o She HAS TO be at home by 11.
Past (debía, tenía que)
o Yesterday I HAD TO go to hospital
o Last week she HAD TO take care of
her grandmother
o
•

6. LACK OF OBLIGATION
•
Present/ future (no es necesario que, no hace falta
•
Past (no era necesario que, no hacía falta que)
que)
o I NEEDN'T write to my mother because I'm going to
see her tomorrow
o I DON'T HAVE TO be in the office until 10 am
o She DOESN'T HAVE TO take her children to school,
because there is a school bus
o
o
I DIDN'T HAVE TO go to the office until 10 am
We DIDN'T HAVE TO bring our books today
because we were going to see a film

7. PROHIBITION
•
Present/ future (no se debe, no se puede, está
•
Past (no se podía, estaba prohibido)
prohibido)
o You MUSTN'T smoke in public places
o You CAN'T drive over 50 Km/hour in urban areas
o
o
We COULDN'T vote in last year's elections because
we were 17 years old.
They COULDN'T work in the USA because they
didn't have a work permit

8. ADVICE
• Present/ future (deberías, no deberías)
o
You SHOULD go to the doctor if you
don't feel well
o
You SHOULDN'T be late
o
You OUGHT TO ask the teacher if you
don't understand the exercise

9. ADVICE
•
Past: Para expresar consejo en pasado hay que usar el verbo
modal + infinitivo perfecto (have + past participle)
–
You SHOULD have gone to the doctor if you didn't feel well
(deberías haber ido al médico si no te sentías bien)
–
You SHOULDN'T have arrived late
( no deberías haber llegado tarde)
–
You OUGHT TO have asked the teacher if you didn't
understand the exercise (deberías haberle preguntado al
profesor)

10. PERMISSION/ REQUEST
•
Present/ future (puedo, podría)
You CAN use the computer if you need it
o You MAY use the computer if you need it
o CAN I open the window, please?
o COULD/ MAY I open the window, please?
o
•
Past (podía, pude)
When I was a child I COULD stay out as long as I
wanted. My parents were very flexible
o Yesterday Mr. Thomson COULD take the day off work
because his wife was in hospital
o

11. ABILITY
•
Present/ future (saber, poder, ser capaz)
o
o
o
•
I CAN speak three languages
I AM ABLE TO speak three languages
I CAN'T speak Japanese
Past (sabía, podía, era capaz)
o
o
o
I COULD ride a bike when I was 6
She HAS BEEN ABLE TO learn German in ten
months
You COULDN'T read when you were 2 years old

12. SOME PRACTICE
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