Rebirth in Buddhism refers to the teaching that the actions of a sentient being lead to a new existence after death, in an endless cycle called saṃsāra. This cycle is considered to be dukkha, unsatisfactory and painful. The cycle stops only if moksha (liberation) is achieved by insight and the extinguishing of craving. Rebirth is one of the foundational doctrines of Buddhism, along with karma, Nirvana and moksha. Rebirth was however less relevant among early Buddhist teachings, which also mentioned the beliefs in an afterlife, ancestor worship, and related rites. The concept varies among different Buddhist traditions.