Modals

Can / Could

We use can and the infinitive for abilities and to say something is possible or permitted:

The negative of can is can't:

CAN (-)	Contraction (-)
cannot	can't

The past of can is could:

can (present)	can (past)
can	could

Subject	could	Infinitive		Time Phrase
I	could	swim	50m	last year.
You	could	get	a 6 month visa	2 years ago.
He	could	sing	well	when he was young.
She	could	take	10 days holiday	last month.
We	could	see	it	yesterday.
They	could	play	in the street	50 years ago.

The negative (-) of could is couldn't:

COULD (-)	Contraction (-)
could not	couldn't

Subject	couldn't	Infinitive		Time Phrase
I	couldn't	swim	well	when he was young.
You	couldn't	get	a 3 month visa	last year.
He	couldn't	sing	it	last week.
She	couldn't	take	any holiday	last month.
We	couldn't	see	it	yesterday.
They	couldn't	play	computer games	50 years ago.

Can and could come before the subject for questions:

CAN	Subject			Yes/No	Subject	CAN
Can	you	swim well?	⇒	Yes,	I	can.
Could	you	swim well last year?	⇒	Yes,	I	could.

For closed questions (yes and no answers):

Positive (+)	Negative (-)
Yes, I can.	No, I can't.
Yes, you could.	No, I couldn't.

CAN	Subject			Yes/No	Subject	CAN
Can	you	swim well?	⇒	Yes,	I	can.
Can	you	swim well?	⇒	No,	I	can't.
Could	you	swim well last year?	⇒	Yes,	I	could.
Could	you	swim well last year?	⇒	No,	I	couldn't.

Now try the quiz below!