A system requires that all the parts have some interdepending relationship among them. E.g., marbles in a sack because one marble has no interdepending relationship with others. A clock is a system because all the gears and springs have interdepending relationships. No way, because all the parts have lost interdepending relationships. Systems Thinking is a paradigm, language, method and set of technologies for building and sharing an understanding of things and processes made up of interdependent relationships.
Systems thinking recognizes that every parts are interconnected.
Input and Output environment Let's shift a focus on single part of a system that we call a stock. The input and output are not free flow. These are regulated by regulator. Things that regulate either input or output. The regulator does not have to be a separate entity.