Grammar notes: ability
Can and could
Can and could are modal verbs. They are sometimes called modal auxiliaries because they are generally used with another verb and help us to understand that verb.
Examples of this auxiliary use are:
I can swim ability
Can I smoke?
Could you lend me £5? asking for something
In this section I’ll only be looking at the ‘ability’ aspect of can and could.
General characteristics of can and could
They do not add -s in the 3rd person singular:
I can swim.
He can swim.
They could all drive before I could.
He could drive before I even had a bike.
To make a question you don’t have to use an auxiliary verb, just invert the subject and the modal verb:
Can you swim?
Can he swim?
Could she read when she was three?
To make a negative sentence, add not or n’t to the modal verb:
I can’t swim (or I cannot swim. Cannot is one word)
Can’t you swim?
We couldn’t finish the exam in time.