Structural functionalism, or simply functionalism, is "a framework for building theory that sees society as a complex system whose parts work together to promote solidarity and stability".
This approach looks at society through a macro-level orientation, which is a broad focus on the social structures that shape society as a whole, and believes that society has evolved like organisms. This approach looks at both social structure and social functions. Functionalism addresses society as a whole in terms of the function of its constituent elements; namely norms, customs, traditions, and institutions.
A common analogy, popularized by Herbert Spencer, presents these parts of society as "organs" that work toward the proper functioning of the "body" as a whole. In the most basic terms, it simply emphasizes "the effort to impute, as rigorously as possible, to each feature, custom, or practice, its effect on the functioning of a supposedly stable, cohesive system". For Talcott Parsons, "structural-functionalism" came to describe a particular stage in the methodological development of social science, rather than a specific school of thought.
In sociology, classical theories are defined by a tendency towards biological analogy and notions of social evolutionism:
Functionalist thought, from Comte onwards, has looked particularly towards biology as the science providing the closest and most compatible model for social science. Biology has been taken to provide a guide to conceptualizing the structure and function of social systems and analyzing evolution processes via mechanisms of adaptation ... functionalism strongly emphasises the pre-eminence of the social world over its individual parts (i.e. its constituent actors, human subjects).
While one may regard functionalism as a logical extension of the organic analogies for societies presented by political philosophers such as Rousseau, sociology draws firmer attention to those institutions unique to industrialized capitalist society (or modernity).