"A system element is a discrete part of a system that can be implemented to fulfill specified requirements. A system element can be a discrete component, product, service, infrastructure, system, or enterprise. A system element can be implemented by hardware, software, data, humans, processes (e.g., processes for providing service to users), procedures (e.g., operator instructions), facilities, materials, and naturally occurring entities (e.g., water, organisms, minerals), or any combination."
"Each system element may be a system. The recursive nature of the term system element conveniently allows the term system to apply equally when referring to a discrete component or a large, complex, and geographically distributed system of systems."