/
ˈdʒuːvənʌɪl/
adj.
  - for or relating to young people, birds, or animals.
- childish.
n.
 a young person, bird, or animal. 
▸Law  a person below the age at which ordinary criminal prosecution is possible (18 in most countries).
Derivative
- juvenility
 /-ˈnɪlɪti/
 n.
- juvenilize
 or juvenilise v.
Etymology
C17: from L. juvenilis, from juvenis ‘young, a young person’.