Environment

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 non-technical contexts, such as politics, it often refers to the natural environment, that part of the natural world that is deemed valuable or important by human beings, for any reason.
In literature, history, and sociology, it is the culture that an individual lives or was educated in, and the people and institutions with whom he interacts; see social environment.
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.
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.
In thermodynamics, it refers to any objects that are not part of the system under study, and may receive or provide heat to it; see surroundings (thermodynamics).
In chemistry and biochemistry, it is the chemical nature of a solution in which a reaction takes place, chiefly its pH (i.e. whether it is acidic or alkaline).
In metallurgy and ceramics, it often refers to the oxidizing or reductive character of the gases or flames prevailing during some high-temperature process.
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.
- In functional programming, lambda calculus, and programming languages, it usually means identifiers that are defined outside a given function but can be used in it. In other words, everything with global or otherwise non-local scope to that function.
- In certain operating systems like Unix, DOS, and Microsoft Windows, the environment is a set of environment variables in the form of var=value used by applications and libraries to affect default preferences.
- More generally, it may also mean the hardware and operating system on which a program is executed; see System platform.
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.)

See also