The term system often sounds too theoretical, ambiguous and we use it in many ways. 

For clarity purposes therefore Ulanowicz, Goerner and Lietaer rather used the term “network”, and defined a system as a network of elements in flow of energy, matter and information. 

Examples: Monetary system, water system, Internet, health care system

Money flows in the monetary system, water flows in the water system, information flows in the Internet, in a country’s health care system we can see the flow of Corona patients, as the stream of people infected by that virus flow through doctors, hospitals, clinics, etc. With these streams of matter we can also see flow of energy and information (like for Corona hospital budgets and information on diagnosing, testing, tracking lines of contamination etc.)

Living systems 

A living system has two special features: it organizes and creates itself, serving one purpose: to sustain it. To survive.

Even we as individuals organize ourselves - continuously adapting as required to survive.

And we re-create ourselves continuously: we renew our skeleton every 10 years, intestines every 15 years, liver every 2 years, skin every 2 weeks. 

This clarity of terms is essential

Sustainability is a system’s property. To understand a non-sustainable situation, we must both identify the system we wish to understand and the flow we wish to make sustainable.