成年的：adult, grown-up, grown

未成年的：minor

年长的：elderly, older in age

上了年纪的：old, advanced in age

老年的：aged

中年的：middle-aged

年轻的：young

青年的：childish

少年的：adolescent

十来岁的：teenage

儿童的：childish

婴儿的：babyish

刚出生的：newborn

年逾古稀的：be past/over seventy of age

年逾花甲的：be past/over sixty years of age

年尊：be advanced in age

年事已高：be advanced in age

青春年少：be in one’s tender youth

年少气盛：be young and spirited

年老体衰：get old and decrepit

年老体弱：be worn with age/ be advanced in age and poor in health

年近半百：be in the neighborhood of fifty/ be about fifty years of age

年近花甲：be close on sixty years of age

年高望重：be full of ages and honor

年富力强：be young and strong, be in the full vigor of life