The Upanishads (/ʊˈpʌnɪʃʌdz/; Sanskrit: उपनिषद्, IAST: Upaniṣad, pronounced [ˈupɐniʂɐd]) are Sanskrit texts of the late Vedic and post-Vedic periods that "document the transition from the archaic ritualism of the Veda into new religious ideas and institutions" and the emergence of the central religious concepts of Hinduism. They are the most recent addition to the Vedas, the oldest scriptures of Hinduism, and deal with meditation, philosophy, consciousness, and ontological knowledge. Earlier parts of the Vedas dealt with mantras, benedictions, rituals, ceremonies, and sacrifices.
While among the most important literature in the history of Indian religions and culture, the Upanishads document a wide variety of "rites, incantations, and esoteric knowledge" departing from Vedic ritualism and interpreted in various ways in the later commentarial traditions. The Upanishads are widely known, and their diverse ideas, interpreted in various ways, informed later traditions of Hinduism. The central concern of all Upanishads is to discover the relations between ritual, cosmic realities (including gods), and the human body/person, postulating Ātman and Brahman as the "summit of the hierarchically arranged and interconnected universe", but various ideas about the relation between Atman and Brahman can be found.
