A “System” is a somewhat vaguely-defined term. Some say anything composed of >1 interacting parts are “systems”. Others have higher thresholds. Some say systems are mental constructs, others say they only exist in the real world. Long story short, the definition sucks, is abstract, and arguable in every instance.
One definition I like:
Any set of related parts for which there is sufficient coherence between the parts to make viewing them as a whole useful. - SEBoK pg 95
There’s also a Systems Poem written by an economist.
Another definition:
A regularly interacting or interdependent group of items forming a unified whole - Webster’s New Collegiate Dictionary
Features of Systems
- Systems may be Open (interacting with an environment) or Closed.
- They may be natural or man-made.
- Systems have (and are arguably defined by) boundaries.
- Systems have a purpose, a reason for existing.
- They have components. They contain connections between these components.
- They often have System Stocks, which are subject to flows into, out of, or within the system.
Systems exhibit System Complexity and Emergent Behavior. Patterns of behavior occur within systems that are not attributable to any one component, but only emerge out of the interactions between them. These types of patterns may be common to different types of systems. These are called archetypes in Systems Thinking parlance. One example of a common system archetype that forms across all types of domains is that of the Hierarchy. Problems that exist across one hierarchy often will show up across others.
