What is System?

Legal Definition
A system is a set of interacting or interdependent component parts forming a complex or intricate whole. Every system is delineated by its spatial and temporal boundaries, surrounded and influenced by its environment, described by its structure and purpose and expressed in its functioning.

Alternatively, and usually in the context of complex social systems, the term is used to describe the set of rules that govern structure or behavior.
-- Wikipedia
Legal Definition
1. Detailed procedures, methods and routines to carry out an activity, problem solve or perform a duty. 2. Purposeful organized structure that is regarded as a whole and consists of interdependent and interrelated elements.