ability n.能力，本领，能耐；专门技能。
（辨析）普通用词，主要用于人，指在智力或体力上能够做某事的实际能力，常后接动词不定式或介词in／for。
〔例证〕a player of great ability极有才华的球员She has the ability to run her father's business.她有能力经营父亲的企业。
He shows an ability in／for farming.他显示出农耕方面的才能。
capability n.能力，才能。
〔辩析〕尤指完成有难度的事情所需的能力，常后接动词不定式或介词of，可以复数形式出现。
〔例证〕manufacturing capability 生产能力
She has the capability to handle the work.她具备处理这项工作的能力，Mary has the capability of becoming an excellent teacher.
玛丽有能力成为一名出色的教师。
In her opinion,simultaneous translation is beyond his capabilities.
她认为他做不了同声传译。
capacity n.能力，才能；容纳能力。
〔辨析〕指人理解或做某事的能力，或容器、房间等的容纳能力，常后接介词of／for。
〔例证〕a child's capacity for learning 孩子的学习能力
He has a capacity for computers.他具有操作计算机的能力。
The fuel tank has a capacity of 50 litres．这个油箱能装50升油。
competence n.能力，胜任。
〔辨析〕强调做某事的非凡能力，常后接介词in。
〔例证〕You should try to maintain your professional competence.
你应当尽力保持自己的专业能力。
We have doubt about his competence in teaching.
我们怀疑他教书的能力。
He demonstrated thorough competence in dealing with these issues.
他在处理这些问题时完全显示出了他的能力。