|feather (fě'ər) Pronunciation Key
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One of the light, flat structures that cover the skin of birds. A feather is made of a horny substance and has a narrow, hollow shaft bearing flat vanes formed of many parallel barbs. The barbs of outer feathers are formed of even smaller structures (called barbules) that interlock. The barbs of down feathers do not interlock. Evolutionarily, feathers are modified scales, first seen in certain dinosaurs.