The word prejudice refers to prejudgment: making a decision before becoming aware of the relevant facts of a case or event. The word has commonly been used in certain restricted contexts, in the expression 'racial prejudice'. Initially this is referred to making a judgment about a person based on their race, religion, class, etc., before receiving information relevant to the particular issue on which a judgment was being made; it came, however, to be widely used to refer to any hostile attitude towards people based on their race or even by just judging someone without even knowing them. Subsequently the word has come to be widely so interpreted in this way in contexts other than those relating to race. The meaning now is frequently "any unreasonable attitude that is unusually resistant to rational influence". Race, sex, ethnicity, sexual orientation, age, and religion have a history of inciting prejudicial behaviour.

Forms of prejudice

Bob J. Farley classified prejudice into three categories. Cognitive Prejudice refers to what people believe is true. An example of cognitive prejudice might be found, for example, adherence to a particular metaphysical or methodological philosophy to the exclusion of other philosophies that may offer a more complete theoretical explanation. Affective Prejudice refers to what people like and dislike. An example of affective prejudice might be found, for example, in attitudes toward members of particular classes such as race, ethnicity, national origin, or creed. Conative Prejudice refers to how people are inclined to behave. Conative prejudice is regarded as an attitude because people don't act on their feelings. An example of conative prejudice might be found in expressions of what should be done if the opportunity presented itself. These three types of prejudice are correlated, but all need not be present in a particular individual. Someone might believe a particular group possesses low levels of intelligence, but harbour no ill feelings toward that group. A group might be disliked because of intense competition for jobs, but still recognize no differences between groups.

'Discrimination' is a behaviour (an action), with reference to unequal treatment of people because they are members of a particular group. Farley also classified discrimination into three categories. Personal / Individual Discrimination is directed toward a specific individual and refers to any act that leads to unequal treatment because of the individual's real or perceived group membership. Legal Discrimination refers to "unequal treatment, on the grounds of group membership, that is upheld by law." Apartheid is an example of legal discrimination, as are also various post-Civil war laws in the southern United States that legally disadvantaged negros with respect to property rights, employment rights and the exercise of constitutional rights. Institutional Discrimination refers to unequal treatment that is entrenched in basic social institutions resulting in advantaging one group over another. The Indian caste system is an historical example of institutional discrimination. As with prejudice generally, these three types of discrimination are correlated and may be found to varying degrees in individuals and society at large. Many forms of discrimination based upon prejudice are outwardly acceptable in most societies.