Modals of Ability

ABILITY

Present Can + (V) Can’t/Cannot + (V)

= am/is/are able to + (V)

I can finish my assignment soon.

I can’t understand this Maths problem.

Past Could + (V) (general ability)

Was/were able to + (V) (on a particular occasion)

I always thought I could understand Maths, but yesterday I was not able to work out what the teacher meant.

Negative Couldn’t + (V) (both for general ability and for particular occasions)

I couldn’t understand the Physics teacher all last year.

Yesterday I couldn’t understand this year’s teacher, although I generally can.

All other tenses Use: be able to + (V)

I have been able to keep up with my studies so far.

I hope I will be able to pass these exams.