The following is a glossary of common English language terms used in the description of birds—warm-blooded vertebrates of the class Aves and the only living dinosaurs, characterized by feathers, the ability to fly in all but the approximately 60 extant species of flightless birds, toothless, beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart and a strong yet lightweight skeleton.
Among other details such as size, proportions and shape, terms defining bird features developed and are used to describe features unique to the class—especially evolutionary adaptations that developed to aid flight. [Source: Wikipedia 
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