The nature of systems
A systems approach involves placing as much emphasis on identifying and describing the connections between objects and events as on identifying and describing the objects and events themselves.
Systems are patterns of cause and effect relationships. These can be simple and unidirectional or they may be linked together in long chains. Any one factor can exert a control function (causing a change in another) and a dependent function (being changed by another) - this is called multi-factoriality.
Chains of cause and effect can be circular so that control function eventually becomes its own dependent function - this is called a feedback loop - and the influences can be either positive, when it causes an increase in the original effect, or negative, when it causes a decrease in the original effect.
Some of the more important defining characteristics of systems are emergence, hierarchical control and communication.