The higher of the two kinds of voices usually belonging to adult males; hence, the part in the harmony adapted to this voice; the second of the four parts in the scale of sounds, reckoning from the base, and originally the air, to which the other parts were auxillary.
A person who sings the tenor, or the instrument that play it.
Specifically, one of the smaller drones that extend away from the bass and the piper's head. More generally, any part that has to do with a tenor, e.g. "a set of drone reeds is a bass and two tenors ."