aged這個字的用法問題?

HE IS 20 AGED=HE IS AT THE AGE OF 20.
(1)aged adj.---aged 5/20 etc(+between)---The school course is open to children aged 5 and over.
The school boy aged 20 years.He is aged 20.
(2)aged adj.very old:-eg:-my aged parents
old=the aged:-old people:-eg:-the care of children and the aged are taken care of by the social welfare.
(3)a difficult/awkward age is used mainly about the time when people /students are teenagers=aged 16
retirement age=aged 65.
school age=aged 5
school leaving age=aged 18
the marrying age=30=aged 30 etc.

aged：…歳的 例1. a man aged 40 years (40歳的男人) 例2. He is aged(adj.) 20. (他是20歲。)←←這是文法，類似“lesson 4” (第4課)。