Ludwig Bertalanffy describes two types of systems: open systems and closed systems. The open systems are systems that allow interactions between its internal elements and the environment. An open system is defined as a "system in exchange of matter with its environment, presenting import and export, building-up and breaking-down of its material components."[1] For example, living organism. Closed systems, on the other hand, are considered to be isolated from their environment. For instance, thermodynamics applies to closed systems. The idea of open systems was further developed in systems theory. For instance, open systems in systems theory encourage a non-representational and non-referential posthumanist approach that actualize complexity of reality in a non-deterministic framework.

Rajeev Kaula has written:

'An open intelligent information systems architecture' -- subject(s): System design, Information technology, System theory

Examples of system theory include general systems theory, cybernetics, chaos theory, and complexity theory. These theories focus on understanding the interactions and dynamics within complex systems, such as ecosystems, organizations, or social networks. They help explain how systems adapt, evolve, and self-regulate.

The main goal of social groups is to discover social group systems. It investigates both the principles common to all complex entities, and the open systems are those that interact with the environment, while closed.

Open systems are computer systems that gives some combination of interoperability, portability, and open software standards. While in physics an open system is a system in which energy can be lost or gained from the environment.