Although the term racism usually denotes race-based prejudice, violence,dislike, discrimination, or oppression, the term can also have varying and contested definitions. Racialism is a related term, sometimes intended to avoid these negative meanings. According to the Oxford English Dictionary, racism is a belief or ideology that all members of each racial group possess characteristics or abilities specific to that race, especially to distinguish it as being either superior or inferior to another racial group or racial groups.  Based on this evidence, "racial characteristics" logically cannot exist either, such as group differences in eye color or human hair color.
The Merriam-Webster's Dictionary defines racism as a belief that race is the primary determinant of human traits and capacities and that racial differences produce an inherent superiority or inferiority of a particular racial group, and that it is also the prejudice based on such a belief. The Macquarie Dictionary defines racism as: "the belief that human races have distinctive characteristics which determine their respective cultures, usually involving the idea that one's own race is superior and has the right to rule or dominate others."
The concept that discrimination can be based on "race" presupposes the existence of "race" itself. However, the US Government's Human Genome Project has announced that the most complete mapping of human DNA to date indicates that there is no distinct genetic basis to racial types. Based on this evidence, "racial characteristics" logically cannot exist either, such as group differences in eye color or human hair color.
According to the Human Genome Project, skin color does exist as a matter of science. So, that which is commonly referred to as "racism" could be more scientifically referred to as "skin color-aroused discrimination". The term "skin color aroused discrimination" has the benefit that it is based on verifiable science, is not based on disproved notions of science, and does not perpetuate a false belief in the disproved concept of biological "race".
The UN does not define "racism", however it does define "racial discrimination": according to the United Nations Convention on the Elimination of All Forms of Racial Discrimination,
the term "racial discrimination" shall mean any distinction, exclusion, restriction or preference based on race, colour, descent, or national or ethnic origin which has the purpose or effect of nullifying or impairing the recognition, enjoyment or exercise, on an equal footing, of human rights and fundamental freedoms in the political, economic, social, cultural or any other field of public life. '
This definition does not make any difference between prosecutions based on ethnicity and race, in part because the distinction between the two remains debatable among anthropologists. According to British law, racial group means "any group of people who are defined by reference to their race, colour, nationality (including citizenship) or ethnic or national origin".
Some sociologists have defined racism as a system of group privilege. In Portraits of White Racism, David Wellman has defined racism as "culturally sanctioned beliefs, which, regardless of intentions involved, defend the advantages whites have because of the subordinated position of racial minorities". Sociologists No�l A. Cazenave and Darlene Alvarez Maddern define racism as "...a highly organized system of 'race'-based group privilege that operates at every level of society and is held together by a sophisticated ideology of color/'race' supremacy. Sellers and Shelton (2003) found that a relationship between racial discrimination and emotional distress was moderated by racial ideology and public regard beliefs. That is, racial centrality appears to promote the degree of discrimination African American young adults perceive whereas racial ideology may buffer the detrimental emotional effects of that discrimination. Racist systems include, but cannot be reduced to, racial bigotry,".
Source: ChinaStones - http://china-stones.info/free-essays/accounting/racism.php