Wiktionary
n. 1 interdisciplinary field of science, which studies the nature of complex systems in nature, society and science, and studies complex parts of reality as systems. 2 systematic study of the complex interactions in systems 3 collection of methods on the development and organization of complex systems.
Wikipedia
Systems theory or systems science is the interdisciplinary study of systems in general, with the goal of discovering patterns and elucidating principles that can be discerned from and applied to all types of systems at all nesting levels in all fields of research. It can reasonably be considered a specialization of systems thinking or as the goal output of systems science and systems engineering, with an emphasis on generality useful across a broad range of systems (versus the particular models of individual fields).
A central topic of systems theory is self-regulating systems, self-correcting through feedback. Self-regulating systems are found in nature, including the physiological systems of our body, in local and global ecosystems, and in climate and also in human learning processes (from the individual on to international organizations like the UN).
Usage examples of "systems theory".
Mental coadunation, whatever it was, supposedly jibed nicely with what Denis called systems theory.
The new theories that had given birth to holism quantum mechanics, batesonian epistemology, general systems theory, cybernetics and information theory had grown into elaborate, intricate systems representing reality with the language and symbols of the universal syntax.