Abstract. There are seven different systems that must be acknowledged and understood by those who purport to do systems engineering. The main system to be engineered is the Intervention System that will be designed to solve a real or perceived problem. The Intervention System will be placed in a Context System and must be developed and deployed using a Realization System. The Intervention, when installed in the Context, becomes the Deployed System which is often different in substantial ways from the original intent of the Intervention. This Deployed System will interact with Collaborating Systems to accomplish its own functions. A Sustainment System provides services and materials to keep the Deployed System operational. Finally, there are one or more Competing Systems that may also solve the original problem and will compete for resources with your Deployed System. All seven systems must be properly reckoned with when engineering a system.