"The cell cycle is like a life cycle. We talk about life cycles as from one generation to the next. Cell cycles are from one cellular generation to the next... in other words, the cell cycle is from when a cell is first born until it divides. Your textbook describes the cell cycle in section 5.1.4, and Figure 5-8 shows their depiction of the cell cycle. I have made my own figure of the cell cycle, and that is shown below. "