Tapas (tapas) in Sanskrit means "heat". In Vedic religion and Hinduism, it is used figuratively, denoting spiritual suffering, mortification or austerity, and also the spiritual ecstasy of a yogin or tāpasa ("...a practitioner of austerities, an ascetic")... The adjective tapasvin means "wretched, poor, miserable", but also "an ascetic, someone practicing austerities."
In the yogic tradition, tapasyā may be translated as "essential energy", referring to a focused effort leading towards bodily purification and spiritual enlightenment. It is one of the Niyamas (observances of self-control) described in the Yoga Sutras of Patanjali. Tapasya implies a self-discipline or austerity willingly expended both in restraining physical urges and in actively pursuing a higher purpose in life. Through tapas, a yogi or spiritual seeker can "burn off" or prevent accumulation of negative energies [karma], clearing a path toward spiritual evolution.