Senescence is a formal and technical word that refers to the state of being old or the process of becoming old.

// Our grandparents, now in their senescence, are enjoying spending more time with family and going on new adventures together.

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“Pilates provides improvements in core strength, flexibility and balance, even when done just once a week. It can help with stress relief, as well as anxiety and depression. Among those 60 years of age and older, Pilates has even been shown to slow the process of senescence.” — Leah Asmelash, CNN, 7 Sept. 2025

Senescence can be traced back to Latin senex, meaning “old.” Can you guess which other English words come from senex? Senile might (correctly) come to mind, as well as senior. But another one might surprise you: senate. This word for a legislative assembly dates back to ancient Rome, where the Senatus was originally a council of elders composed of the heads of patrician families. There's also the much rarer senectitude, which, like senescence, refers to the state of being old (specifically, to the final stage of the normal life span).