Feudalism: A medieval social and economic system in which peasants were bound to work the land owned by nobles in exchange for protection and limited rights. Peasants were an oppressed group within this system.
Women's Suffrage: The fight for women's right to vote during the late 19th and early 20th centuries. Women were historically an oppressed group denied political participation.
Apartheid: A policy of racial segregation enforced by the government of South Africa between 1948 and 1994, resulting in systematic oppression of non-white citizens.