juvenile

Concise Oxford English Dictionary © 2008 Oxford University Press:
juvenile /ˈdʒuːvənʌɪl/

▶adjective

• 1 for or relating to young people, birds, or animals.

• 2 childish.

▶noun a young person, bird, or animal.

■ Law a person below the age at which ordinary criminal prosecution is possible (18 in most countries).

– derivatives
juvenility /-ˈnɪlɪti/ noun,
juvenilize (or juvenilise) verb.

– origin C17: from L. juvenilis, from juvenis ‘young, a young person’.