the.com/juvenile
Old enough to know better, young enough to get away with it.
means Relating to youth, or behavior so immature it embarrasses everyone in the room.
from From Latin juvenilis, meaning youthful, rooted in juvenis, a young person — the same source that gave us junior and rejuvenate.
Legal lineMarks the courts that judge minors separately.
Insult upgradeCalling adults juvenile stings harder than calling them dumb.
Wildlife useBiologists label not-yet-adult animals juveniles too.