"Class" is a subject of analysis for sociologists, political scientists, anthropologists and social historians. However, there is not a consensus on a definition of "class" and the term has a wide range of sometimes conflicting meanings. In common parlance, the term "social class" is usually synonymous with "socio-economic class", defined as "people having the same social, economic, cultural, political or educational status", e.g., "the working class"; "an emerging professional class". However, academics distinguish social class and socioeconomic status, with the former referring to one's relatively stable sociocultural background and the latter referring to one's current social and economic situation and consequently being more changeable over time.
The precise measurements of what determines social class in society has varied over time. Karl Marx thought "class" was defined by one's relationship to the means of production (their relations of production). His simple understanding of classes in modern capitalist society are the proletariat, those who work but do not own the means of production; and the bourgeoisie, those who invest and live off of the surplus generated by the proletariat's operation of the means of production. This contrasts with the view of the sociologist Max Weber, who argued "class" is determined by economic position, in contrast to "social status" or "Stand" which is determined by social prestige rather than simply just relations of production. The term "class" is etymologically derived from the Latin classis, which was used by census takers to categorize citizens by wealth in order to determine military service obligations.
In the late 18th century, the term "class" began to replace classifications such as estates, rank and orders as the primary means of organizing society into hierarchical divisions. This corresponded to a general decrease in significance ascribed to hereditary characteristics and increase in the significance of wealth and income as indicators of position in the social hierarchy.
Historically, social class and behavior were sometimes laid down in law. For example, permitted mode of dress in sometimes and places was strictly regulated, with sumptuous dressing only for the high ranks of society and aristocracy, whereas sumptuary laws stipulated the dress and jewelry appropriate for a person's social rank and station.
Definitions of social classes reflect a number of sociological perspectives, informed by anthropology, economics, psychology and sociology. The major perspectives historically have been Marxism and structural functionalism. The common stratum model of class divides society into a simple hierarchy of working class, middle class and upper class. Within academia, two broad schools of definitions emerge: those aligned with 20th-century sociological stratum models of class society and those aligned with the 19th-century historical materialist economic models of the Marxists and anarchists.