Segregation is the separation of groups of people by custom or by law. It is often based on differences of race, religion, wealth, or culture. Many people consider such differences highly important.

Segregation can occur in almost any area of life. It is particularly evident in housing, education, and employment, and in the use of eating, sleeping, transportation, and other public facilities. Almost all systems of segregation discourage marriage between people of different racial, religious, or social groups. In the United States, for example, many states once outlawed marriage between blacks and whites. But in 1967, the Supreme Court of the United States ruled such laws unconstitutional. Segregation almost always involves some kind of discrimination by one group against another. The term discrimination refers to actions or practices by members of a dominant group that limit the opportunities of a less powerful group.

The term desegregation refers to the process of ending group separation. It generally is used to describe efforts to abolish racial segregation in the United States. The people most affected by racial segregation in the United States have been African Americans.

During the course of desegregation, two or more separated groups may begin to act toward each other in new, friendlier ways. This new relationship between the groups is called integration. A desegregated situation becomes integrated when people from different groups accept and become friendly toward one another.

Segregation is not limited to the United States nor to bias against racial minorities. It has been practiced in various forms in many countries throughout history.