From The Art and Popular Culture Encyclopedia
The middle class, in colloquial usage, consists of those people who have a degree of economic independence, but not a great deal of social influence or power. The term often encompasses merchants and professionals, bureaucrats, and some farmers and skilled workers.
Social hierarchies, and their definitions, vary. There are many factors that can define the middle class of a society, such as money, behavior and heredity. In some countries, it is predominantly money that determines an individual's position in the social hierarchy. In others, other social factors may have as strong an influence. Such factors include education, professional or employment status, home ownership, or culture.
Connotations attached to the term also vary significantly between and within different countries. In the United States of America usage is increasingly broad in scope, but almost always positive in intent (see American middle class).