senescence

Etymology

From Latin senēscere (“to grow old”).

noun

1. (biology) The state or process of ageing, especially in humans; old age.
   Organized shuffleboard has always filled me with dread. Everything about it suggests infirm senescence and death: it’s like it’s a game played on the skin of a void and the rasp of the sliding puck is the sound of that skin getting abraded away bit by bit. 1997, David Foster Wallace, “A Supposedly Fun Thing I'll Never Do Again”, in A Supposedly Fun Thing I'll Never Do Again, Kindle edition, Little, Brown Book Group
   Over the next 150 years the known age of the Earth expanded a millionfold and lost worlds of the past were found to have overflowed with species now gone. The chain stretched, aged, and eventually succumbed to senescence. 2012, Lydia Pyne, Stephen J. Pyne, chapter 6, in The Last Lost World, Penguin
2. (cell biology) Ceasing to divide by mitosis because of shortening of telomeres or excessive DNA damage.
   2018, University of Edinburgh, "Liver Study Offers Insights into Hard-to-treat Diseases" (9 March 2018), Drug Discovery & Development. Tests in mice found that inducing senescence in bile duct cells - mimicking the process seen in human bile duct disease - led to liver scarring and damage of liver function.
3. (gerontology) Old age; accumulated damage to macromolecules, cells, tissues and organs with the passage of time.
4. (botany) Fruit senescence, leading to ripening of fruit.
5. (cytology, of a cell) Condition when the cell ceases to divide.