Asana is a body position, typically associated with the practice of Yoga

Yoga

Yoga is a physical, mental, and spiritual discipline, originating in ancient India. The goal of yoga, or of the person practicing yoga, is the attainment of a state of perfect spiritual insight and tranquility while meditating on Supersoul...

, originally identified as a mastery of sitting still, with the spine as a conduit of biodynamic union. In the context of Yoga practice, asana refers to two things: the place where a practitioner (yogin (general usage); yogi

Yogi

A Yogi is a practitioner of Yoga. The word is also used to refer to ascetic practitioners of meditation in a number of South Asian Religions including Jainism, Buddhism, and Hinduism.-Etymology:...

 (male); yogini

Yogini

Yogini is the complete form source word of the masculine yogi- and neutral/plural "yogin." Far from being merely a gender tag to the all things yogi, "Yogini" represents both a female master practitioner of Yoga, and a formal term of respect for a category of modern female spiritual teachers in...

 (female)) sits and the manner (posture) in which he/she sits. In the Yoga sutras

Yoga Sutras of Patanjali

The Yoga Sūtras of Patañjali are 194 Indian sūtras that constitute the foundational text of Rāja Yoga. Yoga is one of the six orthodox āstika schools of Hindu philosophy, and Rāja Yoga is the highest practice....

, Patanjali

Patañjali

Patañjali is the compiler of the Yoga Sūtras, an important collection of aphorisms on Yoga practice. According to tradition, the same Patañjali was also the author of the Mahābhāṣya, a commentary on Kātyāyana's vārttikas on Pāṇini's Aṣṭādhyāyī as well as an unspecified work of medicine .In...

 suggests that asana is "to be seated in a position that is firm, but relaxed" for extended, or timeless periods.

As a repertoire of postures were promoted to exercise the body-mind over the centuries, to the present day when yoga is sought as a primarily physical exercise form, modern usage has come to include variations from lying on the back

Savasana

-Etymology:The name comes from the Sanskrit words Shava meaning "corpse", and Asana meaning "posture" or "seat".-Description:...

 and standing on the head

Sirsasana

Sirsasana, Shirshasana, Sirshasana , or Headstand, is an asana.In the Supported Headstand , the body is completely inverted, and held upright supported by the forearms, while the crown of the head rests lightly on the floor.Sirsasana is nicknamed "king" of all the yoga poses.-Etymology:The name...

, to a variety of other positions.