Could Vs Was / Were able to

Can-Could / Am-Is-Are...Was-Were Able to are mostly used in a similar way, however there are some rules and differences.

1. To talk about an ability in the present, we use “can” or “be able to”

I can / am able to speak 2 languages.
He can / is able to swim.
My brother isn't able to drive a car

2. To talk about a general ability in the past, we use “could” or “was / were able to”.

I could / was able to run very fast.
I could / was able to jump so high.

3. However; when we talk about a specific success in the past, we should only use “was / were able to”.

Since the exam was difficult, only a few students could / were able to pass it. (managed to pass it)

Mozart ---- compose little pieces of music even when he was 5.
(General ability)

a) can   *b) could   *c) was able to   d) is able to

We ---- reach to the top of the hill before it got dark yesterday.
(Specific success in the past)

a) can   b) could   *c) were able to   d) aren't able to


There is no difference between them when used in a negative sentence.

Because of the great financial difficulties, John couldn't / wasn't able to finish his university education.

4. We use “can” instead of “be able to” in passive forms.

This game --- (play) by 2 or more players.

*a) can be played
b) is able to be played