He has been able to speak English for ten years. (Present Perfect)
He was able to speak good English when he was a child. (Simple Past)
He will be able to speak English even better when he stays in England for some time. (Future)
He should be able to speak English well, because he has been living in England for six years. (With other modals)
He had been able to speak English for five years when he went to England. (Past Perfect)

4) "Can" yapılması mümkün olan olayları ifade ederken de kullanılır.
I'm very busy now, so I can't help you.
(It's not possible for me to help you now.)

I'll finish my work in an hour, so I can help you then.
(It's possible for me to help you after I finish my work.)

I have very little money on me now, so I can't lend you any.
(It's not possible for me to lend you any money now.)

I'll go to the bank in the afternoon, and I'll withdraw some money from my bank account. Then I can lend you some.
(It will be possible for me to lend you some money after I've withdrawn some from the bank.)

5) "Can", birine bir şey yapması için izin verilirken de kullanılır. Bu kullanımıyla, "can", "may" ile aynı anlamı verir.

(The shop owner to the customer)
- You can/may leave your purchases here until you finish your shopping. Then you can come and get them.

(Mother to her daughter)
- Because tomorrow is a holiday, you can/may stay up late tonight.

(Father to his son)
- You can /may go on your date in my car if you wish.

(The teacher to the students)
- Those who finish answering the questions can/may leave the classroom.

6) "Can" in past biçimi "could", "be able to" nun past biçimi ise "was/were able to" dur.
I could run very fast when I was a child.
I was able to run very fast when I was a child.
Some students in my previous class could/were able to speak English almost fluently, but they weren't so good at grammar.

"Could", geçmişteki yeteneklerimizi ya da geçmişte birine izin verme gibi durumları ifade ederken kullanılır.

Mozart could play the piano when he was only four, (ability in the past)
My grandfather was very strong. He could lift enormous boxes on his own. (ability in the past)
It was raining heavily. We could go out only when it stopped raining.
(permission in the past)
(It became possible for us to go out only when the rain stopped.)
Because there was a holiday the next day, the children could stay up late.
(permission in the past)
(It became possible for them to stay up late because there was a holiday the next day.)

"Was/were able to" da. geçmişteki yeteneklerimizi ya da geçmişteki izin verme durumlarını ifade ederken kullanılır. Ancak, "geçmişte zor bir durumun üstesinden gelme" anlamı (manage to do), sadece "was/were able to" ile ifade edilir. "Could" bu anlamda kullanılmaz.