Answer: Even today, most Indian languages use the term "jati" for the system of hereditary social structures in South Asia. When Portuguese travelers to 16th-century India first encountered what appeared to them to be race-based social stratification, they used the Portuguese term "casta" — which means "race" — to describe what they saw. Today, the term "caste" is used to describe stratified societies based on hereditary groups not only in South Asia but throughout the world.
According to one long-held theory about the origins of South Asia's caste system, Aryans from central Asia invaded South Asia and introduced the caste system as a means of controlling the local populations. The Aryans defined key roles in society, then assigned groups of people to them. Individuals were born into, worked, married, ate, and died within those groups. There was no social mobility.