Juvenile, a.
Etymology: [L. juvenilis, from juvenis young; akin to E. young: cf. F. juvénile, juvénil. See Young.]
1. Young; youthful; as, a juvenile appearance. "A juvenile exercitation." Glanvill.
2. Of or pertaining to youth; as, juvenile sports.
Syn. -- Puerile; boyish; childish. See Youthful.
1 other Webster entry under this spelling
Juvenile, n.
A young person or youth; -- used sportively or familiarly. C. Bronté.
Shades of meaning
Fernald has no entry of its own for juvenile; he lists it under new, youthful.
Where he writes about it:
Juvenile and youthful are commonly used in a favorable and kindly sense in their application to those still young; youthful in the sense of having the characteristics of youth, hence fresh, vigorous, light-hearted, buoyant, may have a favorable import as applied to any age, as when we say the old man still retains his youthful ardor, vigor, or hopefulness; juvenile in such use would belittle the statement. — from youthful