System, scheme, network, complex, organism, economy can mean an organized integrated whole made up of diverse but interrelated and interdependent parts.
System usually implies that the component units of an aggregate exist and operate in unison or concord according to a coherent plan for smooth functioning.
Scheme may replace system but tends to stress an overall design for the interrelation of components, often a design carefully calculated or planned detail, but sometimes scheme may carry a suggestion of irony or depreciation that is absent from system (see also PLAN ).
Network suggests a system with interconnection or intercrossing at salient points sometimes involved but susceptible to analysis or control.
Complex stresses an elaborate interweaving, interconnection and interrelationship of components difficult to trace.
Organism basically applies to systems having life, but it is sometimes extended to systems felt as analogous to biological systems (as in capacity for growth and development).
Economy implies a system concerned with needs and their regulation and fulfillment by individual, species, household, business, or government.