Usa

Ang usa (Ingles: deer) ay isang uri ng hayop na namumuhay sa bundok at gubat. Venison (Ingles) ang karneng nakakain mula sa usa. Tinatawag na libay (Ingles: doe o hind) ang babaeng usa, samantalang barako naman (Ingles: roebuck o hart) ang lalaking usa.^[2]

Usa[1] Temporal na saklaw: Early Oligocene–Recent PreЄ Є O S D C P T J K Pg N
Images of a few members of the family Cervidae (counterclockwise from top left): the elk (Cervus canadensis), white-tailed deer (Odocoileus virginianus), grey brocket (Mazama gouazoubira), barasingha (Rucervus duvaucelii), pudú (Genus: Pudu), sika deer (Cervus nippon), red deer (Cervus elaphus), and reindeer (Rangifer tarandus)
Klasipikasyong pang-agham
Dominyo:	Eukaryota
Kaharian:	Animalia
Kalapian:	Chordata
Hati:	Mammalia
Orden:	Artiodactyla
Infraorden:	Pecora
Pamilya:	Cervidae Goldfuss, 1820
Tipo ng genus
Cervus Linnaeus, 1758
Subfamilies
Capreolinae Cervinae
Combined native range of all species of deer.