Religious tradition originating in the Indian subcontinent, with wide internal variation and numerous sects; also known in scholarship as Brahmanism. The term Hindu was first used by medieval Persian invaders for people living east of the Indus River. The term ‘Hinduism’ was popularised in the 19th century by British colonial scholars and Indian social reformers such as Ram Mohan Roy and Swami Vivekananda, to refer to a modernised form of Brahmanism with a greater emphasis on theistic devotion. Hinduism may describe the more elite, caste-based forms of Brahmanical practice or may also include heterodox traditions such as Bhakti or Tantra. Caste — both the adherence to it and the struggle against it — may be considered a unifying theme of Hinduism across sects. Different strands of Hinduism derive variously from the Vedas, Upanishads, Puranas, Dharma Shastras and other Sanskrit texts, but there is no singular text or historical figure considered foundational to the tradition.