idiom: act your age (act one’s age)
— Our 12-year old refuses to act her age and continues to suck her thumb.
— When you start acting your age—instead of like a five year-old—we'll let you use the car.
— I need a vacation. At home, I have three boys under the age of six, plus my husband refuses to act his age.
— My grandchildren act their age with us and then go back home and make their parents' lives living hell.
— My son never acted his age. He always behaved like an adult until he got married.
— As Prince sang, "Act your age, not your shoe size!"
— Why does your girlfriend always talk like a whiny baby? I wish she'd act her age.
— Our daughter cannot ever act her age in public and we have to do something about it.
This idiom is included in singer/songwriter Prince's song, "Kiss":
Women, not girls, rule my world
I said they rule my world
Act your age, Mama!
Not your shoe size
(Not your shoe size)
Maybe we could do the twirl
(You can hear him sing the idiom around minute 2:50 in the video above)
He adds a funny twist to tell people to not act like their shoe size, which is normally much smaller than a person's age.
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