I've seen the term 'young adult' bandied around lately to refer to people in their 20's, which seems odd to me, because when I was a teenager, that term referred to teens. I can't decide if people are using it more accurately now or it's a sign of the increasing de-maturation of society. On the other end of the spectrum, I feel like there isn't a good term for people who are past middle aged. Unless someone specifically refers to themselves first as 'an old man/woman', it's not a term I'd use for anyone under 80 and even then I might argue with the person. My parents are close to 70 now. They are clearly not middle aged, but to me the term 'old' implies a certain frailty and loss of power that certainly doesn't apply to them. So my husband and I have started referring to them and people in that age group as elders: wise people who have lived for a significant amount of years, but are far from over the hill.