class

In biological classification, a subdivision of phylum and forms a group of related orders. For example, all mammals belong to the class Mammalia and all birds to the class Aves. Among plants, all class names end in ‘idae’ (such as Asteridae) and among fungi in ‘mycetes’; there are no equivalent conventions among animals. Related classes are grouped together in a phylum.

class

In sociology, the main grouping of social stratification in industrial societies, based primarily on economic and occupational factors, but also referring to people's style of living or sense of group identity.

Within the social sciences, class has been used both as a descriptive category and as the basis of theories about industrial society. Theories of class may see such social divisions either as a source of social stability (Emile Durkheim) or social conflict (Karl Marx).

In the USA, social scientists use measurements of education level, income, and occupation to ascribe social strata. Class, however, is not an important defining characteristic for most Americans. Most identify themselves as middle class, though more specific attributions such as ‘upper-middle class’ and ‘lower-middle class’ are also common.

class

In mathematics another name for a set.