One of the outer flight feathers of birds, which originate from the manus. Most non-passerines have 10 primaries. Ciconiidae (storks), Phoenicopteridae (flamingos), and Podicipedidae (grebes) have 12; Ardeidae (herons), Anatidae (ducks, geese, etc.), and some other groups have 11. Most passerines have nine functional primaries, the tenth being reduced.
Subjects: Zoology and Animal Sciences.