1) A normal series of events in a cell that leads to its death.

2) Programmed cell death, the body's normal method of disposing of damaged, unwanted, or unneeded cells.

3) Apoptosis is the process of programmed cell death. It is used during early development to eliminate unwanted cells; for example, those between the fingers of a developing hand. In adults, apoptosis is used to rid the body of cells that have been damaged beyond repair. Apoptosis also plays a role in preventing cancer. If apoptosis is for some reason prevented, it can lead to uncontrolled cell division and the subsequent development of a tumor.