response: Oh I see.  When an organism's single cells stop dividing, it's called cellular senescence, which is an ageing process.
original_response: Aging can refer to single cells within an organism that has ceased dividing..
history: I really dislike getting to be old. Do you?  There's an accumulation of changes over time when one ages.  They include psychological, social, and physical changes. Tell me about it, I can't remember things now. Aw.  How's your reaction time?  I can slow with age. That is why I no longer drive, I'm too slow.
knowledge: In the broader sense, ageing can refer to single cells within an organism which have ceased dividing (cellular senescence) or to the population of a species (population ageing).