Benchmark 11A
Common Themes: Systems
Grades 6-8, page 265

Thinking about things as systems means looking for how every part relates to others. The output from one part of a system (which can include material, energy, or information) can become the input to other parts. Such feedback can serve to control what goes on in the system as a whole.

See the general discussion in Unifying Concepts and Processes: Systems, order, and organization.