MODAL VERBS

Question 1

ABILITY

Answer 1

can, could, and be able to
can (present and future) and could (past) are used for general ability to do something. Can is also used to refer to an ability to do something specific at a time in the future.
Can and could refer to the ability to do sth but not to the doing of it. Can and be able to are used to talk about ability.
We use will be able to to talk about ability + achievement of the action.
We use will be able and not can to talk about skills that will be acquired in the future.
(we use can + be + adjective or noun to talk about possibility)
We use be able to when it is grammatically impossible to use can.
We use can, could and could have in conditional sentences, and in implied conditions.

Question 2

CERTAINTY, POSSIBILITY AND DEDUCTION

Possibility

Answer 2

can, could, may, might, must, will, should, ought to

To talk about something that is possible to do at any time, we use can and may.
To talk about Future possibility, we use may or might (we can also use could when it refers to a theoretical possibility)
To talk about possibility in the present, we use may, might or could + simple infinitive of continuous infinitive.
To talk about possibility in the past, we use may, might, or could + perfect infinitive (simple or continuous)

Question 3

CERTAINTY, POSSIBILITY AND DEDUCTION

Deduction

Answer 3

To make a deduction about something in the present, we use must (positive) or can’t (negative) + simple infinitive or continuous
To make a deduction about something in the past, we use must or can’t + perfect infinitive simple or continuous

To make assumptions we can use should/ought to + present infinitive for the present or should/ought to + perfect infinitive for the past.

Question 4

CERTAINTY, POSSIBILITY AND DEDUCTION

Certainty

Answer 4

To talk about a present or a future certainty, we use will + simple or continuous infinitve

Question 5

OBLIGATION, NECESSITY, PERMISSION, SUGGESTIONS AND ADVICE

Advice

Answer 5

—should, ought to, must, have to, have (got) to, need, can, can’t, may, may not, mustn’t, shall we…?, we could…, would you like to…?—

To give advice, use should or ought to. Should is more frequently used than ought to. These modals indicate that a course of action is a good idea. We often use them with “i think, don’t you think or do you think…”

To give strong advice and recommendations we use must. Must can refer to the present or the future.

To criticize actions in the Past!, we use should/ought to + have + perfect infinitive

Question 6

OBLIGATION, NECESSITY, PERMISSION, SUGGESTIONS AND ADVICE

Obligation

Answer 6

To talk about obligation, use must, mustn’t or have to
(Have to isn’t a modal but it can be used in any form)
Must and have to are often similar and interchangeable, but there is a difference:

Have to: the obligation is often external, it comes from the situation
Must: the obligation comes from the speaker and it’s imposed by the speaker.

We can also use have got to to express obligation. Have got to is often interchangeable with have to but there is a difference:

Have to can be used for habitual actions & single actions.
Have got to should only be used for single actions.

To express a Negative Obligation we use mustn’t, not don’t have to (this is lack of obligation)

To express obligation in the Past, we use Had To!

Question 7

OBLIGATION, NECESSITY, PERMISSION, SUGGESTIONS AND ADVICE

Necessity

Answer 7

To express necessity, use need.
We can use need as a modal verb in questions and negatives. It’s more often used in negatives.
We can also use need as an ordinary verb followed by the to-inf.

To express lack of necessity in the past, use needn’t + perfect inf, or didn’t need to/didn’t have to + infinitive. But there is a difference between them:

Needn’t + have + perfect inf: the action wasn’t necessary but it was done anyway.

Didn’t need to/have to: the action wasn’t necessary, so it wasn’t done.

Question 8

OBLIGATION, NECESSITY, PERMISSION, SUGGESTIONS AND ADVICE

Permission

Answer 8

To ask for permission we use can, could, may, might I….? (register). To make a request we use can, could, would you…?

To give or refuse permission, use can/can’t/may/may not/ must/mustn’t

Question 9

OBLIGATION, NECESSITY, PERMISSION, SUGGESTIONS AND ADVICE

Suggestions

Answer 9

To make a suggestion or invitation we use shall we…?, we could…, would you like to…?

Question 10

HABIT

Answer 10

Would and used to

Used to is not a modal verb but it can be used for statements, questions and negatives.
We use would and used to to talk about past habits.

When we use would to talk about a past habit, it is necessary to use a past time reference.
Used to can be used with or without a past time reference.

When we talk about past situations and not actions, we have to use USED TO, not would.