Reference #312: Thinking in Systems
A system is an interconnected set of elements coherently organised in a way that achieves something. It comprises the following components: elements, interconnections, and a function or purpose.
The term "function" is generally generally use for non-human systems and "purpose" for human systems. But this is not an absolute distinction since many systems comprise both human and non-human elements.
Meadows. Thinking in Systems, 2008. (11, 15)