Ability = What a person can do (Qualitative) Capability= Generally refers to ability, Usually refers to what an inanimate object can do Capacity = How much something can contain (Quantitative) ; sometimes used figuratively to indicate a person's mental or physical power

Thanks, Nanren888.

Ariana's answer has the essense of it. These words are sometimes used in almost interchangeable ways and sometime differently. I try to provide some wider examples. I sometimes have the ability to answer questions. = I am able, because I know how (sometimes) My team has the capability to do far more as a team than separately. Can mean "know how", or can mean similarly to capacity, has enough resource. We have little work on, so just now we have the capacity to take on two more jobs. The factor building is larger than we need at the moment. With it, we have the ability to expand capacity without having to move.