necrosis

results from denaturation of intracellular proteins and enzymatic digestion of the lethally injured cell (robbins)

coagulative necrosis

caused by interruption of blood supply
'pale and firm' - structure preserved
e.g. myocardial infarction

liquefactive

pus - dead leukocytes
hypoxic death of CNS cells

gangrenous

necrosis on multiple tissue planes