/'eɪbl; `ebl/
adj be ~ to do sth (used as a modal v 用作情态动词) have the power, means or opportunity to do sth 有能力, 办法或机会做某事; 能
*The child is not yet able to write. 这个孩子还不会写字.
* Will you be able to come? 你能来吗?
* You are better able to do it than I (am). 你比我更有能力做这件事.

/'eɪbl; `ebl/
adj (-r, -st / 5eIblIst; `eblIst/) having knowledge or skill; competent; capable 有知识或技能的; 有能力的; 有本事的
*an able worker 有才干的工作者
* the ablest/most able student in the class 班上最有才华的学生.

adj
[Date: 1300-1400; Language: Old French;Origin:Latin habilis 'skillful', from habere 'to have']
be able to do sth
a) to have the skill, strength, knowledge etc needed to do something
　I've always wanted to be able to speak Japanese.
see usage notecan¹
b) to be in a situation in which it is possible for you to do something
　I'd like to do more gardening, but I never seem able to find the time.
　I haven't been able to read that report yet.
clever or good at doing something
　one of my more able students