When someone holds a certain negative feeling against a person due to a perceived notion against the entire group the person is a member of then such an affective feeling is called as prejudice.
The unfavourable opinion against a person usually is associated based on the political affiliation of the person, sexual orientation, race, religion, caste, beliefs, age etc.
The irrational suspicion or hatered is not based on any actual experience of the person but merely due to a preconcieved idea and thus, holding such an opinion is not considered to be fair.
The unfavourable feeling is usually considered as illogical and hence, it is usually advised that prejudice should not exist in the society.
