The definition of race is primarily that of running as the word comes from the Middle English word ras meaning "to rush". However, although it may be one of the lesser definitions of the word, if one talks about "race" -- without article or pronoun -- the definition that comes to mind is often that of a division of humanity into different groups.
This idea first came into being to separate groups based on observable physical traits in the 1600s and continued in increasing use, and refined definition, through the early 1800s. Although some of the scientists had neutral goals for the use of the division, it was primarily used as a method of justifying colonization and subjugation of one group over another. It is largely discredited as a useful methodology within science at the present time.
In the elementary school that my children attended, there were about 850 children. If you lined up the children according to skin pigmentation, you would have a long continually varying set of shades and colors from near alabaster to ebony. If you lined them up on a summer day, you would get a different ordering of people from that on a winter day. The same thing holds true for color of eyes, or hair, or width of nose. Each physical characteristic varies on a continuous stream -- although there are certainly areas of the world that are more homogenous (similar between individuals) than others. This is why it has been abandoned by science -- it makes no sense to have discrete classifications.
Just because race has no reasonable definition does not mean there is not racism -- bias and prejudice based on observable (or known familial) physical traits. Racism, sexism, religionism, and other bias/prejudice are forms of xenophobia (fear of "the other"). It has existed since the beginning of recorded history and most likely since the rise of consciousness. The only cure for the syndrome is knowledge -- understanding of "the other" such that the similarities become more obvious than the differences. During periods of antagonism and preparation for war, differences are accentuated (made to seem greater) by governments in order to inflame xenophobia and the inclination to distrust and fear.
Some people say that an ism can only take place by the group in greater power toward the group having less power. Thus, there can be no sexism by women having bias or prejudice about men and there can be no bias or prejudice by pigmentally enhanced people towards those who are pigmentally challenged. This makes as much sense as the original xenophobic reaction. If there exists bias or prejudice based on an observable (or known association with a group who DOES have such observable) physical traits then the relation of power makes no difference.
In summary, the best way to work with, and reduce, xenophobia in all of its forms is knowledge and understanding.
