PRESENT AND PAST USE OF MODAL AUXILIARIES

2014

Modal verbs or auxiliaries can express:

Prohibition: Can't, Mustn't, Be not allowed to Permission: Can, Be allowed to. Obligation: Must, Have to Lack of obligation: Don't / Doesn't have to

Modal auxiliaries help other verbs by providing an additional meaning to the main verb of the sentences.

They do not work with conjugations. They use infinitive verbs.

I

We + HAVE TO + Infinitive verb

You DON'T HAVE TO

They

He

She + HAS TO + Infinitive verb

It DOESN'T HAVE TO

They usually are used with all the personal pronouns.

The only exception is the modal Have to.

LET'S LEARN THEIR USES

OBLIGATION: HAVE TO

Have to / Has to is used for external obligation (Imposed

by someone else). Like rules, regulations, etc.

We have to study for our English test on Monday.

(The obligation comes from the teacher)

Its Past Form is HAD TO and it can be used with all the

personal pronouns.

OBLIGATION: MUST

Must is used for internal obligation (Imposed by the speaker

himself or herself). It is always followed by the infinitivr verb

without TO. It can go with all the personal pronouns. And it is

not usually used in questions.

We must study for our English test.

(The speaker thinks it is necessary)

Its Past Form is HAD TO and it can be used with all the

personal pronouns.

LACK OF OBLIGATION: DON'T / DOESN'T HAVE TO

Don't / Doesn't have to is the negative form of Have to or

Has to. It is used when something is not necessary.

Students don't have to wear the school uniform on Friday.

(There's no problem if they want to use it or not

because of 11th grades jean's days activities)

Its Past Form is DIDN'T HAVE TO and it can be used with all

the personal pronouns.

PERMISSION: CAN

Can is the easiest modal auxiliary. It stands for in Spanish

Poder. It can be used with all the personal pronouns and

followed by the infinitive verb without TO.

Its Past Form is COULD .

We could leave school at 1 in the afternoon.

(The principal gave us permission to watch the chilean

Team soccer game at home yesterday)

PERMISSION: BE ALLOWED TO

Be allowed to stands for in Spanish Ser o Estar permitido a.

Be can be replaced by IS – AM – ARE, and according to them

we use the differents personal pronouns.

Its Past Form is WAS / WERE ALLOWED TO.

Was she allowed to have lunch at the café?

(Did she have the permission or not?)

PROHIBITION: MUSTN'T

Even though mustn't is the negative form of must, their uses

are different. Mustn't is used when you are not able to do

something under any circunstance. It can be used with all the

personal pronouns.

Its Past Form is DIDN'T HAVE TO.

We mustn't use our mobile phones in class.

(It is a school regulation)

PROHIBITION: CAN'T

Even though can't is the negative form of can, their uses

are different. Can't is used when you are not able to do

something under any circunstance. It can be used with all the

personal pronouns.

Its Past Form is COULDN'T.

We can't use piercings at school.

(It is a school regulation)

PROHIBITION: BE NOT ALLOWED TO

Even though be not allowed to is the negative form of be

allowed to, their uses are different. Be not allowed to is used

when you are not able to do something under any

circunstance. The use of BE is according to each personal

personal pronoun.

Its Past Form is WASN'T / WEREN'T ALLOWED TO.

We aren't allowed to eat inside the Computer room.

(It is a school regulation)

Material created by Teacher Danitza Lazcano

Flores Teacher of English

Master in Education and

Educational Counselor