The correct answer is Attitude, Belief, Behavior, or Institutional arrangement that favors one race or ethnic group over another.
Racism is any type of discrimination in which one ethnic group is favored over another ethnic group. It may exist in the traditionally understood sense where one race such as Caucasian believes that they are better than another race such as African people, or it can be in the form of two groups belonging to the same race perceiving each other as the worse race which often happened in civil wars in Africa.