1. Belief that the intended function of something should determine its design, construction, and choice of materials, or a 20th-century design movement based on this.
2. Any philosophy or system that gives practical and utilitarian concerns priority over aesthetic concerns.
3. Any doctrine that stresses utility or purpose.
4. The analysis and explanation of social institutions according to the function they perform in society; for example, the family is seen as an institution for social stability and cohesion.

Functionalism is one of the early schools of psychological thought which took as the proper subject matter for psychological study those mental processes or chains of actions that demonstrate a usefulness in the adjustment of the organism to its environment.

The principles of functionalism have been absorbed into the main themes of contemporary psychology.