In Sanskrit, sutra means thread or string. These texts form the last stage of Vedic literature, by different writers between 500 and 200 BC. These works developed as a result of the need to simplify the rites and rituals explained in the Brahmanas. These concise treatises simplify Vedic teachings on rituals and their reasons. They also simplify the concepts of customary law. They are known as the "angas" or limbs of the four Vedas, but are considered smriti.
There are three known groups of text called sutras: Shrautasutras, Grihyasutras and Dharmasutras, together known as the Kalpa Sutra, and are considered attached to the Vedas.