Discrimination is the ability to distinguish one thing from another, often involving a value judgement.
In human social behavior, discrimination is prejudiced treatment or consideration of, or making a distinction towards, a being based on the group, class, or category to which they are perceived to belong.
These include age, caste, criminal record, height, disability, family status, gender identity, gender expression, generation, genetic characteristics, marital status, nationality, color, race and ethnicity, religion, sex and sex characteristics, sexual orientation, social class, species, as well other categories.
Discrimination consists of treatment of an individual or group, based on their actual or perceived membership in a certain group or social category, "in a way that is worse than the way people are usually treated". more info