Dvija (Sanskrit: द्विज) means "twice-born" in ancient Indian Sanskrit. The concept is premised on the belief that a person is first born physically and at a later date is born for a second time spiritually, usually when he undergoes the ritual of passage that initiates him into a school for Vedic studies. The term also refers to members of the three varnas in the traditional Hindu social system, or social classes — the Brahmins (priests and teachers), Kshatriyas (warriors), and Vaishyas (merchants) — whose Sanskara of Upanayana initiation was regarded as a second or spiritual birth.