I wonder if you realize, but usually, calling someone who is currently 80-89 years old has "in his/her/their" in it. For example: - My grandma is now in her eighties. - My grandfather still looks very healthy, even though he's in his eighties. Yet for calling someone who was born in the 80's, sounds different: - My brother was born during the eighties. - Such hippie-like style, she's definitely one of the eighties. The trick here is to first understand the concept, and the right choice of words would come out naturally. Hope this helps. :)

A person who is 80-89 years old is an octogenarian. You can also say "a man in his eighties" or "a woman in her eighties". This is more common. We also use the term "senior citizen" to describe anyone who is over 75.

Your description is correct. for someone born in the 1980s you could say "Im an eighties child" Or ""Im a child of the 80s" or "look at his fashion, hes definitely an eighties kid"