Based on Lippmann’s study, many socio-psychologists define stereotype in different words. Allport (1954), in his classic book The Nature of Prejudice, stated that stereotype is a kind of fixed impressions which is in together with generalization and exaggerates facts. And the function of stereotype is to “justify (rationalize) our conduct in relation to that category.”(Allport, 1954: 191)

In 1981, according to Tajfel, a stereotype was regarded as a specific expression of attitude. “It entails an agreement between members of a single group on certain characteristics, which are accepted as a valid, discriminating means of describing the difference of other groups (the outside)”.

That’s to say, stereotypes are an overgeneralized and oversimplified set of beliefs about a group of people in a certain social category. (Kosslyn and Rosenberg, 2004: 683) they also pointed that a stereotype may be positive, such as “women are nurturing”; neutral, such as “Mexicans eat spicy food”; or negative, such as “Australians drink too much” 

Form all above, the definition of stereotype is clear to us. Stereotype refers to shared conception of the character of a group. A stereotype is a fixed impression which conforms very little to the reality, and results from our defining first and observing second.