an artifact (or system of artifacts) that is instrumental in accomplishing some end

a device for amplifying or transmitting sound

device that enables something to be used in a way different from that for which it was intended or makes different pieces of apparatus compatible

a device that injects fuel into a hot exhaust for extra thrust

a device that causes material to gather into rounded balls

a device that provides reactive force when in motion relative to the surrounding air; can lift or control a plane in flight