'Functionalist' defined

Sociology
Functionalism focuses on the structure and workings of society. Functionalists see society as made up of inter-dependent sections which work together to fulfill the functions necessary for the survival of society as a whole. People are socialized into roles and behaviors which fulfill the needs of society.
Functionalists believe that behavior in society is structural. They believe that rules and regulations help organize relationships between members of society. Values provide general guidelines for behavior in terms of roles and norms. These institutions of society such as the family, the economy, the educational and political systems, are major aspects of the social structure. Institutions are made up of interconnected roles or inter-related norms. For example, inter-connected roles in the institution of the family are of wife, mother, husband, father, son and daughter.

Architecture
Functionalism, in architecture, is the principle that architects should design a building based on the purpose of that building.

The place of functionalism in building can be traced back to the Vitruvian triad, where 'utilitas' (variously translated as 'commodity', 'convenience', or 'utility') stands alongside 'venustas' (beauty) and 'firmitas' (firmness) as one of three classic goals of architecture.
Functionalist views were typical of some gothic revival architects, in particular Augustus Welby Pugin wrote that «there should be no features about a building which are not necessary for convenience, construction, or propriety» and «all ornament should consist of enrichment of the essential construction of the building».

Chicago architect Louis Sullivan popularized the phrase 'form ever follows function' to capture his belief that a building's size, massing, spatial grammar and other characteristics should be driven solely by the function of the building. The implication is that if the functional aspects are satisfied, architectural beauty would naturally and necessarily follow.
'Form follows function' expresses a significant and enduring idea. Sullivan's protege Frank Lloyd Wright is also cited as an exemplar of functional design.

The roots of modern architecture lie in the work of the Franco-Swiss architect Le Corbusier and the German architect Mies van der Rohe. Both were functionalists at least to the extent that their buildings were radical simplifications of previous styles. Le Corbusier famously said "a house is a machine for living in"; his 1923 book Vers une architecture was, and still is, very influential, and his early built work such as the Villa Savoye in Poissy, France is thought of as prototypically functional.(from wikipedia)