What is a system?
A system definition taken from Redesigning Society by Russell Ackoff and Sheldon Rovin
A system is a whole that has one or more defining functions and consists of two or more essential parts that satisfy three conditions
1) the system cannot do without the part to perform its defining function
2) no essential part can affect the system independently,
how it affects the system as a whole depends on its interaction with at least one other essential part of the system
3) no subsystem of a system has an independent effect on the whole