necrosis

Necrosis is when cells die accidentally due to, say, trauma (ex. a poisonous spider bite), or lack of nutrients (ex. lack of blood supply).  Necrosis begins with cell swelling, the chromatin gets digested, the plasma and organelle membranes are disrupted, the ER vacuolizes, the organelles break down completely and finally the cell lyses, spewing its intracellular content and eliciting an immune response (inflammation).

apoptosis

Apoptosis can constitute cell suicide or cell murder.  Cells will commit suicide when they lack any incoming survival signal in the form of trophic factors, or when they detect extensive DNA damage in their own nucleus.  Cells will murder other cells to clear out unneeded cells or to eliminate potentially self-attacking immune cells.
![Apoptosis_DU145_cells_mosaic.jpg](https://steemitimages.com/DQmVUAQ944FZXfcLgZGDRofonLAVMn9nBSXCFMj7X6Hseg5/Apoptosis_DU145_cells_mosaic.jpg)