Racism is the belief in the superiority of one race over another, which often results in discrimination and prejudice towards people based on their race or ethnicity. The use of the term "racism" does not easily fall under a single definition.
The ideology underlying racism often includes the idea that humans can be subdivided into distinct groups that are different due to their social behavior and their innate capacities, as well as the idea that they can be ranked as inferior or superior. Historical examples of institutional racism include the Holocaust, the apartheid regime in South Africa, slavery and segregation in the United States, and slavery in Latin America. Racism was also an aspect of the social organization of many colonial states and empires.
While the concepts of race and ethnicity are considered to be separate in contemporary social science, the two terms have a long history of equivalence in both popular usage and older social science literature. "Ethnicity" is often used in a sense close to one traditionally attributed to "race": the division of human groups based on qualities assumed to be essential or innate to the group (e.g. shared ancestry or shared behavior). Therefore, racism and racial discrimination are often used to describe discrimination on an ethnic or cultural basis, independent of whether these differences are described as racial. According to a United Nations convention on racial discrimination, there is no distinction between the terms "racial" and "ethnic" discrimination. The UN convention further concludes that superiority based on racial differentiation is scientifically false, morally condemnable, socially unjust and dangerous. It also declared that there is no justification for racial discrimination, anywhere, in theory or in practice.
Racist ideology can manifest in many aspects of social life. Racism can be present in social actions, practices, or political systems (e.g., apartheid) that support the expression of prejudice or aversion in discriminatory practices or laws. Associated social actions may include nativism, xenophobia, otherness, segregation, hierarchical ranking, supremacism, and related social phenomena.