I. ˈjü-və-ˌnī(-ə), -n ə l adjective
Etymology: French or Latin; French juvénile, from Latin juvenilis, from juvenis young person — more at young
Date: 1625
1.
a. : physiologically immature or undeveloped : young
b. : derived from sources within the earth and coming to the surface for the first time — used especially of water and gas
2. : of, relating to, characteristic of, or suitable for children or young people
juvenile books
3. : reflecting psychological or intellectual immaturity : childish
II. noun
Date: 1733
1.
a. : a young person : youth
b. : a book for children or young people
2. : a young individual resembling an adult of its kind except in size and reproductive activity: as
a. : a fledged bird not yet in adult plumage
b. : a 2-year-old racehorse
3. : an actor or actress who plays youthful parts