Segregation (emphasis on "a") is synonymous with such words as "separation," "stratification," or "separation."
Most often this word is used in the context of "racial segregation" - a barbaric custom that existed until the XX century in the US, South Africa and some other countries. Blacks were not allowed to travel with white people in the same transport, attend the same schools and receive the same set of public services. In South Africa, the division was called "apartheid". Today, some form of racial, national, sexual and religious segregation can be found in various regions of the world. So, for example, entry into the sacred city of Mecca is allowed only to Muslims.
Segregation is in the list: Society