Editing Open system (systems theory) (section)

{{Short description|Systems with external interactions}}
{{Use American English|date = March 2019}}
[[File:OpenSystemRepresentation.svg|thumb|252px|''Open [[system]]s'' have input and output flows, representing exchanges of matter, energy or information with its surroundings.]]

An '''open system''' is a system that has external interactions. Such interactions can take the form of information, energy, or material transfers into or out of the system boundary, depending on the discipline which defines the concept. An open system is contrasted with the concept of an [[isolated system]] which exchanges neither energy, matter, nor information with its environment. An open system is also known as a flow system.

The concept of an open system was formalized within a framework that enabled one to interrelate the [[Organismic theory|theory of the organism]], [[thermodynamics]], and [[Theory of Evolution|evolutionary theory]].<ref>Luhmann, Niklas. ''Social Systems''. Stanford: Stanford University Press, 1995; pp. 6-7</ref> This concept was expanded upon with the advent of [[information theory]] and subsequently [[systems theory]]. Today the concept has its applications in the natural and social sciences.
[[File:Diagram Systems.svg|thumb|253x253px|Properties of isolated, closed, and open systems in exchanging energy and matter.]]
In the [[natural sciences]] an open system is one whose border is permeable to both [[energy]] and [[mass]].<ref>[http://www.maxwellian.demon.co.uk/faq/glossary.html Glossary] {{Webarchive|url=https://web.archive.org/web/20070817185842/http://www.maxwellian.demon.co.uk/faq/glossary.html |date=2007-08-17 }} Maxwell Demon, 1998.</ref> By contrast, a [[closed system]] is permeable to energy but not to matter. 

The definition of an open system assumes that there are supplies of energy that cannot be depleted; in practice, this energy is supplied from some source in the surrounding environment, which can be treated as infinite for the purposes of study. One type of open system is the [[radiant energy]] system, which receives its energy from [[solar radiation]] &ndash; an energy source that can be regarded as inexhaustible for all practical purposes.