Chapter 7 - Section 7.5 - Programmed Cell Death Is a Necessary Process in Living Organisms - Apply The Concept - Page 147: 1

The difference between necrosis and apoptosis is that apoptosis is a programmed series of events that results in cell death (so the cell intended to die), and necrosis is unplanned/unprogrammed cell death that occurs from mechanical stress, injuries, or oxygen or nutrient starved. Apoptosis occurs when it's no longer needed by the organism, or when it's too old (the older a cell is, the more likely it is to get genetic damage and lead to cancer).

The difference between necrosis and apoptosis is that apoptosis is a programmed series of events that results in cell death (so the cell intended to die), and necrosis is unplanned/unprogrammed cell death that occurs from mechanical stress, injuries, or oxygen or nutrient starved. Apoptosis occurs when it's no longer needed by the organism, or when it's too old (the older a cell is, the more likely it is to get genetic damage and lead to cancer).