Death is defined scientifically as the irreversible cessation of vital bodily functions. Biologically, it is marked by the failure of critical homeostatic mechanisms, most notably the circulatory and respiratory systems. Cellular death can occur due to various processes, including necrosis, which results from acute injury, or apoptosis, a controlled process of programmed cell death used in development and tissue turnover. Overall systemic failure leads to irreversible loss of consciousness and the cessation of metabolic activity. The progression of death involves changes in physiological parameters, from declining levels of oxygenated blood to eventual cardiac arrest, representing the ultimate endpoint of biological function.