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english grammer world

CAN (Auxiliary Verb)

 (1) Ability or knowledge or skill
- If somebody have the ability to do something, we use can in text. And sometimes we use be able to instead of can. Because can have no present perfect and infinitive.
- past tense : was(were) able to
  future tense : will (shall) be able to
  present tense : can or be able to
  present perfect tense : have been able to
- the negative is can't (can not)

(ex) Can you play tennis? No I can't play tennis.
(ex) I can speak Japanese. But I can't speak Spanish.

 (2) permission or ask
- request for permission to do something
- synonym is May

(ex) Can I borrow your pen?

 (3) possibility
(a) in interrogative sentence - Express confusion or strong doubt

Can + S ....? (about present)
Can + S + have + p.p ....? (about past)

(b) in negative sentence - strong possibility

S + cannot .... (about present)
S + cannot have + p.p .... (about past)

(ex a) Can you think the fact be true?
= I think, it is impossible that the fact is true.
(ex b) He can't have done his homework through all that noise.

modals modals modal could