"At least by the time of Albiruni (early 11th century), the word Hindu had a distinct religio-geographical meaning: a Hindu is an Indian who is not a Muslim, Jew, Christian or Zoroastrian. (...) A Buddhist, a Jain, a tribal, they were all included in the semantic domain of the term Hindu. Though the early Muslim writers in India had noticed a superficial difference between Brahmins and Buddhists, calling the latter 'clean-shaven Brahmins', they did not see an opposition between 'Hindus and Buddhists' or between 'Hindus and tribals', nor did later Muslim rulers see an opposition between 'Hindus and Sikhs'. On the contrary, Albiruni lists Buddhists among the idolatrous Hindu sects. (...) India's Constitution does not give a definition of the term Hindu, but it does define to whom the 'Hindu Law' applies. It has to do this because in spite of its pretence to secularism, the Indian Constitution allows Muslims, Christians and Parsis a separate Personal Law. .... Article 25 (2)(b) of the Constitution stipulates that 'the reference to Hindus shall be construed as including a reference to persons professing the Sikh, Jain or Buddhist religion'. The Hindu Marriage Act of 1955 goes in greater detail to define [the term 'Hindu' in legal terms], by stipulating in Section 2 that the Act applies: '(a) to any person who is a Hindu by religion in any of its forms and developments, including a Virashaiva, a Lingayat or a follower of the Brahmo, Prarthana or Arya Samaj, '(b) to any person who is a Buddhist, Jain or Sikh by religion, and '(c) to any other person domiciled in the territories to which this Act extends who is not a Muslim, Christian, Parsi or Jew by religion. This definition of the 'legal Hindu', though explicitly not equating him with the 'Hindu by religion', is exactly coterminous with the original Islamic use of the term Hindu: all Indian Pagans are legally Hindus."