The class of warm-blooded vertebrates that comprises or consists of birds: The Aves characteristically posses forelimbs in the form of wings and hind limbs adapted for perching, swimming, or walking.

Aves are almost completely covered with feathers, and scales are usually present on the feet.

The beak, or bill, is covered with a horny sheath and all of the living Aves are toothless and the heart is four-chambered, and there are extensive air sacs between the visceral organs.

The Aves are oviparous and it is estimated that there are 8600 species which have been described.

2. Etymology: from Latin plural of avis, bird.