minority, nonage, teens, tender age, bloom. cradle, nursery, leading strings, pupilage, puberty, pucelage. prime of life, flower of life, springtide of life, seedtime of life, golden season of life
heyday of youth, school days
rising generation.
Adjectives
young, youthful, juvenile, green, callow, budding, sappy, puisne, beardless, under age, in one's teens
younger, junior
hebetic, unfledged.
Phrases
youth on the prow and pleasure at the helm" [Gray]