Saṃsāra is a Sanskrit word that means "wandering" or "world", with the connotation of cyclic, circuitous change. It is also the concept of rebirth and "cyclicality of all life, matter, existence", a fundamental belief of most Indian religions. In short, it is the cycle of death and rebirth. Saṃsāra is sometimes referred to with terms or phrases such as transmigration, karmic cycle, reincarnation, and "cycle of aimless drifting, wandering or mundane existence".The concept of Saṃsāra has roots in the post-Vedic literature; the theory is not discussed in the Vedas themselves. It appears in developed form, but without mechanistic details, in the early Upanishads. The full exposition of the Saṃsāra doctrine is found in Sramanic religions such as Buddhism and Jainism, as well as various schools of Hindu philosophy after about the mid-1st millennium BC. The Saṃsāra doctrine is tied to the karma theory of Indian religions, and the liberation from Saṃsāra has been at the core of the spiritual quest of Indian traditions, as well as their internal disagreements. The liberation from Saṃsāra is called Moksha, Nirvana, Mukti or Kaivalya.