Difference Between Ability and Capability
Key difference: Ability is the "actual" level of development and capability in the "potential" level of development.
Many believe that ability and capability are synonymous. Some dictionaries even list them as synonyms. However, they are used in different contexts. The definition of ability states that it is the possession of the qualities, necessary skill, competence, or power required to do something, i.e. the ability to cope with a problem. Whereas, the definition of capability states that it is the quality of being capable, i.e. the potential of being able.
Ability is about the present, what a person can currently do. Ability implies possibility.. It relates to a skill or a natural talent. Ability means that one has the necessary skill or talents, to say, play the piano or to run. Ability is the generic, non-quantifiable quality of being able to do something. It is a talent, a natural skill, which can’t be measured.
Capability, on the other hand, implies unrealized potential, i.e. one may be capable if he gains the ability or skill. Capability refers to a maximum ability, one's limits of capacity for doing or accomplishing something. Capability can have a positive or negative implication, such as one might be capable of doing something already, but isn’t doing it because one is not taking action or that one may have the potential to do something, if he gains, develops or refines his skill or ability.
She is able to play the piano. She might even be capable of playing famous compositions.
He is able to run. He is even capable of winning races.