A control offering one choice from a fixed set, where choosing one unchooses the rest. Named for the buttons on a receiver.
Clipped from radio- (a combining form meaning ray), from Latin radius (ray, spoke); the interface control borrows its name from the physical dial of an old receiver, where pressing one button released all the others.
A control offering one choice from a fixed set, where choosing one unchooses the rest. The name remembers the receiver's own buttons — mutually exclusive because only one station can be tuned to at a time.