Expressing Ability

Able To

I am able to write French.

He is able to type fast.

I was able to finish the cleaning by morning.

We were able to finish the test in time.

Not able to 

He is not able to typed fast.

They are not able to come so early.

I was not able to catch the morning train.

Can

I can sew.

I can repair the TV.

I can lend you my car.

Cannot

I cannot remove the stain.

You cannot reach by ten.

She cannot speak English.

Could

Could denotes ability in the past

I could dance gracefully.

She could sing sweetly.

He could make cake very well.

Could Not

I could not cook non-vegetarian.

She could not attend classes last week.

He could not eat well.