Also see definition of "Able" in Word Study
Able
ABLE [isbe]
ABLE - a'-b'-l: The Greek dunamai, "to have power," may refer either to inherent strength, or to the absence of external obstacles, or to what may be allowable or permitted. The Greek ischuo, as in Lk 13:24; Jn 21:6, refers always to the first of the above meanings. The use of the word as an adjective in the King James Version of 2 Cor 3:6, is misleading, and has been properly changed in the Revised Version (British and American) into "sufficient as ministers," i.e. "hath fitted us to be ministers."
Also see definition of "Able" in Word Study