The term "life cycle" implies two things: that a process is perpetual and that the sequence of events is obligatory or uni-directional. There is no beginning or end to a life cycle and the sequence of events cannot change. A seed cannot go directly to being a mature plant nor revert back to the blossom stage.
The Project Management Life Cycle
The term "life cycle" is misleading, because it is neither a perpetual circle of events nor is the sequence of events rigidly fixed. There are five stages to the project management life cycle that usually occur in sequence. During large complex projects it is often necessary to return to planning several times. In this case, the project management life cycle can become very complex with multiple repeats of planning and even initiating processes.
By: Brian Egan