Definitions of complex:

• noun:   a conceptual whole made up of complicated and related parts

  Example: "The complex of shopping malls, houses, and roads created a new town"

• noun:   (psychoanalysis) a combination of emotions and impulses that have been rejected from awareness but still influence a person's behavior
• noun:   a compound described in terms of the central atom to which other atoms are bound or coordinated
• noun:   a whole structure (as a building) made up of interconnected or related structures
• adjective:   complicated in structure; consisting of interconnected parts

  Example: "A complex set of variations based on a simple folk melody"