This is the design worlds favorite term to describe the practical purposes that any design is intended to serve. A chair serves as seating support; a living room as a gathering place for varied activities; a dining room as eating space; an office as work space; a shop as the arena for buying and selling; and so on. In order to be a success, any design must support its function. This goes beyond mere success or failure, becoming a matter of a scale of value in which the level of functional service can be related to the level of design quality.
Almost any chair can be sat in, and any room will serve for living or dining in some way. A truly well designed chair will offer appropriate seating comfort for its intended use. A well-designed room will provide an outstandingly superior setting for its intended function. A well-designed living room, for example, will provide comfortable settings for conversation, solitary Reading, music listening, and TV-watching, as well as a workable setting for entertaining. A dining room will offer space, seating, lighting, and atmosphere suitable to each meal to be taken there, for as few or as many people as may be expected at any one time. An office will provide suitable space for working, equipment, and storage, as well as space to receive visitors and hold small meetings if required. Superior functional.Performance is the first test of design quality. Failure to function well reflects a larger design failure.
In addition to basic, or primary, function, designs must satisfy various secondary functions. Besides providing good seating, for example, a chair should be practical to move, keep clean, repair, and maintain, and its production cost should be appropriate to its intended use. This last issue is so closely linked to the next group of design issues as to leave some uncertainty as to whether it is a functional issue at all. Certainly it ties together matters of function and construction.