An environment is a complex of external factors that acts on a system and determines its course and form of existence. An environment may be thought of as a superset, of which the given system is a subset. An environment may have one or more parameters, physical or otherwise. The environment of a given system must necessarily interact with that system.
Generally, the environment or milieu of some object or action consists of the substances, circumstances, objects, or conditions by which it is surrounded or in which it occurs. (Although the two terms are usually synonyms, some sciences prefer the less common milieu to avoid confusion with the more well-known meanings of environment in ecology, politics, and sociology.)
Either word may be used with specialized meaning in various contexts:
In biology, Environment may be defined as the complex of climatic, biotic, social and edaphic factors that acts upon an organism and determines its form and survival. It, therefore, includes everything that may directly affect the metabolism or behavior of a living organism or species, including light, air, water, soil, and other living beings. See environment (biology).
In architecture, ergonomy, and work safety, it is the ensemble of elements of a room or building that affect the well-being and efficiency of its occupants—including dimensions and arrangement of living spaces and furniture, light, ventilation, temperature, noise, etc..; see living environment .
See geography for a subject that is a study of the environment. (Terms like SOSE (Studies of Society & the Environment) not only refer to environmental studies, but also social sciences.)
In psychology, environmentalism is the theory that environment (in the general and social sense) plays a greater role than heredity in determining an individual's development.
In fiction, especially science fiction and fantasy it can refer to any fictional universe or setting in which different stories are set. Thus the Star Wars sagas are all in one milieu while the various Star Trek series, movies, and books are in a different milieu. This meaning is also relevant to fantasy roleplaying games.
In any kind of organization or enterprise, it may also refer to the social and psychological conditions that are felt by its members; see work environment .
In any kind of meeting or congress, it may signify the prevailing mood or preferences of the participants.
Computer science and informatics
In computer science, it generally means data, processes or devices which, although not explicitly named as parameters of a computation, may nevertheless affect its outcome.