A Sanskrit term used to designate in Hinduism, Jainism, and Mahāyāna Buddhism a vast class of texts of a didactic, mnemotechnic character. The word sūtra, originally meaning "thread," is found in the upanishads in the sense of "a short treatise, to be learned by heart." A first group of sūtras, called as a whole "Supplement to the Vedas," is devoted respectively to phonetics, ritual, grammar, etymology, metrics, and astronomy, all disciplines that are necessary for reciting the sacred hymns correctly. In addition, and less dependent on the hymns, there are the great sūtras on ritual: (1) Shrauta-sūtras, dealing with the great sacrifice, in which three fires or more are necessary; (2) Shulva-sūtras, which give the rules of measuring the place of sacrifice, of building the altar, etc.; (3) Grhya-sūtras, dealing with the daily duties of man and personal rites from conception to death and burial; (4) Dharmasūtras, expounding the priestly and secular law.
The last group of Hindu sūtras has a philosophical character. Each of the four systems of Hindu philosophy in its classical age has its own sūtras: (1) The Vaisheshika-sūtras aim at liberating man by revealing to him the principle of his self. (2) The Nyāya-sūtras, although concerned with logic, also aim at liberating man by fighting error. (3) The sūtras called Samkhyakarika deal with physics. (4) The Yoga-sūtras are concerned with mental concentration.
See Also: hinduism; jainism; buddhism; indian philosophy; and the bibliographies at the end of these articles.