The idea of the caste system is that it is a [categorial hierarchy] (https://www.bbc.co.uk/news/world-asia-india-48619734) of the Hindu religion, which places Brahmins (priests and teachers) on top, followed by Kshatriyas (rulers/warriors), Vaishyas (farmers, traders and merchants), and Shudras (labourers). There is also an unofficial fifth group of 'Outcastes' of people who do 'unclean' work outside of the four categories. The Indian caste system was hereditary and people could only marry within the same caste. Thus, the caste system had many characteristics of 'race'. Some of the castes were small-scale [tribal groups] (https://www.britannica.com/topic/race-human/Indias-caste-system) who incorporated into the Hindu kingdoms, and therefore there were in fact, thousands of castes in India. The caste system was changed by British colonial authorities who were perpetuating ideas about Indian society. British authorities gave the [Brahmans] (https://victorianweb.org/history/empire/india/caste.html) certain special privileges that the other groups did not have and elevated their status. The goal of the British was to form India into a more 'Westernised' society. However, due to European theories of race in the 19th century, Britain used the caste system as a classification of race. [Scientific analysis] (https://www.britannica.com/topic/race-human/Indias-caste-system) that was taken seriously at the time indicated that 'Bengali upper castes were Aryan in origin' and the lower castes were destined to 'die out'. Therefore, Britain reinvented the Indian caste system into a classification of race which has created long-lasting issues of colourism in India.