Asceticism is classified into two types. "Natural asceticism" consists of a lifestyle where material aspects of life are reduced to utmost simplicity and a minimum but without maiming the body or harsher austerities that make the body suffer, while "unnatural asceticism" is defined as a practice that involves body mortification and self infliction of pain such as by sleeping on a bed of nails.
Asceticism has been historically observed in many religious traditions, including Buddhism, Jainism, Hinduism, Christianity, and Judaism. Contemporary mainstream Islam has lacked asceticism, except for the minority Sufism whose long tradition has included strict asceticism. The practitioners of these religions abandoned sensual pleasures and led an abstinent lifestyle, in the pursuit of redemption, salvation or spirituality. Asceticism is seen in the ancient theologies as a journey towards spiritual transformation, where the simple is sufficient, the bliss is within, the frugal is plenty.
The adjective "ascetic" derives from the ancient Greek term askēsis, which means training or exercise. The original usage did not refer to self-denial, but to the physical training required for athletic events. Its usage later extended to rigorous practices that are used in all major religious traditions, in varying degrees to attain redemption and higher spirituality.
Asceticism has been classified into natural and unnatural forms of asceticism. "Natural asceticism" is defined as a lifestyle where material aspects of life are reduced to utmost simplicity and minimum. This may include minimal, simple clothing, sleeping on floor or caves, eating simple minimal amount of food. Natural asceticism, state Wimbush and Valantasis, does not include maiming the body or harsher austerities that make the body suffer. In contrast, "unnatural asceticism" is defined as a practice that goes further, and involves body mortification, punishing one's own flesh, and habitual self infliction of pain such as by sleeping on a bed of nails.
Self-discipline and abstinence in some form and degree are parts of religious practice within many religious and spiritual traditions. Ascetic lifestyle is associated particularly with monks, nuns, fakirs in Abrahamic religions, and bhikkhus, munis, sannyasis, yogis in Indian religions.