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System Definitions


by MCS

version 1.3  29 October  2019




System, and its plural—systems, is an overloaded term in the English language. We ascribe many different meanings to this term depending on the context in which it appears. Some familiar examples of its descriptive use include:


Transportation Systems

Metric System

Security System

Dewey Decimal System

Computer Systems

Systems Analysis

Systems Engineering

Systems Biology

Endocrine System

Solar System


Environmental System

Classification System

Management System


On this site the term system will take on a very specific meaning.  By the term system we will mean simply a network of relations.


system is a network of relations.


The definitions of both a network and a relation will require a bit of explanation. We will take up the study of networks and relations early on. These studies are described in the MCS Process page of the Introductory Materials.



 Complex Systems

The term complex system implies that systems in general exhibit a significant range of structure and behavior. We will focus on a system's structural aspects in order to declare it complex. We will define a complex system as a network of relations  containing feedback loops. The nature of feedback will be a topic that we will take up in our study of networks.


complex system is a network of relations containing feedback loops.


The difficulty posed by feedback structures in a system is that they can precipitate a circular chain of events. The results can be especially disconcerting if we have intentionally modified a relation at some link in a chain only to find that same relation returned to its initial value, or pushed even further in an unwanted direction by the existing system.


The human body is filled with feedback networks of a biochemical nature whose sole purpose is to maintain a given chemical equilibrium. The endocrine system is one that is particulary sensitive to chemical imbalances. For example, trying to adjust thyroid hormone imbalances by adding or suppressing thyroid related homones, often leads to feedback induced reactions that counter the intended therapy.



Complex Adaptive Systems

We can take our systems analysis one step further by defining complex adaptive systems. Complex adaptive systems are able to modify both the nature and number of their own networked relations. As such, they have the ability to react to changes in their environment by changing their own structure and behavior.


complex adaptive system (CAS) is a network of relations containing feedback loops that is able to modify both the nature and number of its own relations.


All systems that we classify as being biologically alive are complex adaptive systems. In addition, software systems that exhibit autonomous learning are classified as being CAS. How times change. It wasn't long ago that software capable of modifying itself was considered anathema, and needed to be rewritten in order to obviate that behavior.


The human biosystem is the best example of a complex adaptive system. Problems that arise in this context are some of the most difficult we will face in a lifetime. Cancers create self adapting systems that are resistant to intervention because these system adapt themselves to resist the nature of an intervention. Mindful of such egregious tenacity and the importance of the outcomes, we have chosen to focus our attention on this website on problems associated with the human biosystem.