in social sciences, theory based on the premise that all aspects of a society--institutions, roles, norms, etc.--serve a purpose and that all are indispensable for the long-term survival of the society. The approach gained prominence in the works of 19th-century sociologists, particularly those who viewed societies as organisms. The French sociologist Émile Durkheim argued that it was necessary to understand the "needs" of the social organism to which social phenomena correspond. Other writers have used the concept of function to mean the interrelationships of parts within a system, the adaptive aspect of a phenomenon, or its observable consequences. In sociology, functionalism met the need for a method of analysis; in anthropology it provided an alternative to evolutionary theory and trait-diffusion analysis.

A social system is assumed to have a functional unity in which all parts of the system work together with some degree of internal consistency. Functionalism also postulates that all cultural or social phenomena have a positive function and that all are indispensable. Distinctions have been made between manifest functions, those consequences intended and recognized by participants in the system, and latent functions, which are neither intended nor recognized.

The British anthropologist A.R. Radcliffe-Brown explored the theoretical implications of functionalism as a relationship between a social institution and the "necessary conditions of existence" of a social system. He saw the function of a unit as the contribution it makes to the maintenance of a social structure--i.e., the set of relationships among social units.

In an attempt to develop a more dynamic analysis of social systems, the American sociologist Talcott Parsons introduced a structural-functional approach that employs the concept of function as a link between relatively stable structural categories. Any process or set of conditions that does not contribute to the maintenance or development of the system is said to be dysfunctional. In particular, there is a focus on the conditions of stability, integration, and effectiveness of the system.