not able to do something 没有能力（做某事） - incapable of something
incapable of speech 不会说话 - incapable of doing something
The children seem to be totally incapable of working by themselves. 孩子们好像完全不能靠自己做功课。
Extra ExamplesHe was apparently physically incapable of lowering his voice. 看来他就是天生大嗓门，根本低不下来。 She was constitutionally incapable of bad temper. 她天生不会发脾气。 The wine had made him incapable of thinking clearly. 葡萄酒下肚，他就无法清醒地思考了。
Oxford Collocations Dictionaryverbs- appear
- be
- feel
- …
- absolutely
- completely
- quite
- …
- of
- incapable of something
not able to control yourself or your affairs; not able to do anything well 不能克制自己的；不能自理的；什么事也做不好的 He was found lying in the road, drunk and incapable. 他被发现躺在路上，烂醉如泥。 If people keep telling you you're incapable, you begin to lose confidence in yourself. 如果人们不断地对你说你无能，你就开始失去自信心了。 This type of arrangement remains valid even if you become mentally incapable. 哪怕你精神失常，这种协议也仍然有效。
Oxford Collocations Dictionaryverbs- appear
- be
- feel
- …
- absolutely
- completely
- quite
- …
- of
opposite capable
Word Originlate 16th cent.: from French, or from late Latin incapabilis, from in- ‘not’ + capabilis (from Latin capere ‘take or hold’).