be able to 后跟动词原形，表示具体的能力，与can意思相近。

I am not able to /can't answer your question.

我回答不了你的问题。

Are you able to type?

你会打字吗？

He wasn't able to /couldn't understand the true meaning of life.

他当时不能理解生活的真正意义。

be able to 的用法

was/were able to的用法

was/were able to 表示过去成功的做了某事，相当于managed to do sth.或succeeded in doing sth.

The maths problem was hard but I was able to work it out .

这道数学题虽然难，但我把它做出来了。

The traffic was heavy,but I was still able to get home on time .

交通拥挤，但我依然按时到家了。


be able to 的其它用法

Will you be able to come tomorrow ?

你明天能来吗？

I'm sorry I haven't been able to answer your letter in time .

真不好意思，我没能及时给你回信。