noun, の adjective
An elderly person is an old person (or an elderly person). Don't call a person a 古い人, though. 古い is used for things, not people. Be nice, they're your elders.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
senior citizens' club
In Japan, more and more elderly people are living alone or in pairs.
Did you patch things up with that elderly person?
Wow! That old man is such a hunky beefcake.