A group, population, breed, or variety within a species, although because of difficulties in its definition race is rarely used in a scientific context.

Race is also sometimes used to divide humanity into different groups according to real or imagined common descent. Such divisions are usually based on physical characteristics, such as skin and hair colour, and shape of eyes and nose, which are related to the geographical origins of a particular group. In the 19th century, it was believed that human beings could be unambiguously classed as members of particular races, and that social and cultural differences could be explained on racial grounds. In the early 20th century the anthropologist Franz Boas claimed that racial typing on a physical basis was arbitrary and argued the cultural origin of psychological differences. His approach became generally accepted, though the Nazis, who produced entirely false theories of race, burned his book. Human variation continues to be studied but the notion of ‘race’ as a useful system of classification has largely been abandoned.

Racism is the spurious belief that human characteristics and abilities are determined by race or ethnic origin. Racism, like religious intolerance, has been the cause of much human strife and warfare throughout history. Imperialistic and militarily dominant peoples have usually justified their actions by believing themselves to be superior to the peoples they have conquered or enslaved. The Greek and Roman empires were built by the labour of slaves and the European empires, including the British Empire, also relied on slavery and the destruction and dispossession of indigenous peoples. Within Europe the Jews were persecuted for centuries, in the 20th century suffering the Holocaust. Six million Jews were exterminated by the Germans between 1939 and 1945 because the Germans had been indoctrinated to believe that they were racially superior to non-Aryans. Between 1948 and 1994 the policy of apartheid attempted to separate Black and White people to prevent interbreeding in South Africa. In the second half of the century civil wars accompanied by genocide and ‘ethnic cleansing’ have cost thousands of lives in Bosnia and Herzegovina, Serbia, Rwanda, and Burundi.

In spite of the scientific disregard for the concept of race, racism continued throughout the 20th century to provide an ominous threat to many ethnic minorities. However, in Britain and elsewhere race-relations acts have outlawed blatant racial discrimination and encouraged a more tolerant attitude to differences in cultural and ethnic origins.