I. un·able |ən+ adjective
Etymology: Middle English, from un- (I) + able, adjective
1. : not able : incapable
the sun is unable to melt the snow down to this underlying part — American Guide Series: New Hampshire
2.
a. : unqualified , incompetent , inefficient
b. : impotent , helpless
like an unable phoenix in hot ashes — Time
II. un·a·ble ˌəˈnābəl transitive verb
Etymology: Middle English unablen, probably from un- (II) + ablen to enable — more at able
: disable , incapacitate
so unabled by the gout that she cannot dress herself — Samuel Johnson