What term describes the process of programmed cell death?

The process of programmed cell death is referred to as apoptosis. This is a highly regulated and organized process that cells undergo as part of normal physiological functions, such as development and maintenance of tissue homeostasis. During apoptosis, cells undergo characteristic changes, including cell shrinkage, chromatin condensation, and DNA fragmentation, ultimately leading to the cell's death. This method of cell death is advantageous because it allows for the removal of damaged or unwanted cells without provoking an inflammatory response, unlike necrosis, which is typically a pathologic process resulting from injury or insult.

In contrast, other terms indicated in the question represent different cellular processes. Cellular senescence refers to the process by which cells cease to divide and grow, often in response to stress or DNA damage, and is associated with aging and tissue repair. Cellular differentiation is the process by which a less specialized cell becomes a more specialized cell type, essential for the development of multicellular organisms. Necrosis is a form of uncontrolled cell death usually resulting from injury, leading to inflammation and damage to surrounding tissues. Thus, apoptosis is specifically defined as programmed cell death, distinguishing it from these other biological processes.