Acting as auxiliaries

Modal + bare-infinitive

Never changing forms (no -s, -ed or -ing)

Used with progressive (be + v-ing) and perfect (have + p.p) aspects

Can/Could => ability

May/Might => permission

Will/Would => prediction

Shall => prediction

Should/Ought => escapable obligation or duty

Must => inescapable obligation

Needn't => absence of obilgation

Can/Could => natural or learned ability

E.g. Can you run 1500 meters in 5 mins?

Can you drive a car?

Jim could run very fast when he was a boy.

Barbara couldn't sing very well when she was younger.

Be (un)able to

Be (in)capable of

Manage to

Succeed in

Could/Was/Were able to => acquisition of a skill after effort

E.g. I tried again and found I could/was able to swim

Was/Were able to, managed to, succeeded in => specific achievement in the past (happening for only 1 time)

E.g. In the end they managed to rescue the cat on the roof. (...couldn't rescue the cat...)

Can/Could + verb of perception (NOT be able to)

Could ~ would be able to => “unreal past” (unreal/ unlikely situations NOT in the past)

Could have/ would have been able to => ability not used due to personal failure or lack of opportunity

E.g. I'm sure you could get into university (if you applied).

I could slap your face.

(not) be allowed to

(not) be permitted to

Be forbidden to

Be not to

Very polite…

• Can/could I (possibly)…

• Do you think I could/might use your phone?

• I wonder if I could/might…

• Might I (possibly) be allowed to…?

A certain fact

A possibility

• She could/may/might be at home (Perhaps _{British accent}/Maybe _{American accent} she’s at home)

Past possibility

• A certain fact

• A possibility

Less common for possibility

Question about possibility

E.g. May/Might this be true?

Might/Could he know the answer?

Certainty/ Facts

Deduction

E.g. He must live here./ He must be leaving.

He can’t live here/ He can’t be leaving.

He must have lived here./ He must have been leaving.

I’m sure that he lives/lived here

I’m sure it rained last night <- It must have rained last night.

I’m sure it didn’t rain last night <- It can’t/couldn’t have rained last night.

Request with things/substances

• Request with action

  • Will/Would you (kindly) open the door for me (please)? (about willingness)

  • Can/could you (possibly) open the door (please)?  (about ability)

  • Would you mind opening the window for me (please)?

• Response

  • Yes, of course

  • No, I’m afraid I can’t

  • Not at all, no problem

Suggestions/Invitations with actions

Offers with action

“Should”: it’s advisable to/ it’s (my) duty to

“Ought to” slightly stronger than should, regulations or duties imposed from the outside

“Had better”: the strongest (some specific future action) + threat/warning/urgency

“Have to”: inescapable obligation coming from outside (a regulation, an order from somebody, etc)

“Have got to”: frequently used in writing ~ have to

“Must”:  inescapable obligation coming from the speaker (or the hearer in the questions)

Advisability/ Necessity in the past

• I should have been at the office before 9.

• I ought to have left/ have been leaving London before 9.

Lack of necessity

Inadvisability

He will always complain if he gets the opportunity

When we were students we would often stay up all night

Jackie used to make all her own dresses.