A bird or birds.
[Greek ornis, ornith-, bird.]
The scientific study of birds is ornithology; an ornithopod (Greek pous, pod-, foot, hence ‘bird-footed’) is a mainly bipedal herbivorous dinosaur; the adjective ornithischian (Greek iskhion, hip joint) denotes herbivorous dinosaurs of an order distinguished by having a pelvic structure resembling that of birds. An ornithopter (Greek pteron, wing) was a machine designed to achieve flight by means of flapping wings. The amino acid ornithine was given that name because it is related to a substance first found in bird excrement.