The system life cycle comprises a series of stages that represent the various states a system undergoes, beginning with the identification of need and concluding with complete decommissioning. It constitutes a finite set of general phases and stages through which a system progresses during its lifetime.
The life cycle of a system refers to its evolution over time, beginning with the initial concept and ending with retirement (GOST R ISO/IEC 15288-2005).
A life cycle is defined not as a period of existence, but as a process involving sequential changes in state, determined by the actions performed (R 50-605-80-93).