youthful(s = adj.all) vernal, young - suggestive of youth; vigorous and fresh; "he is young for his age"
Derived form noun youthfulness1
1. Not yet mature or aged; young. Shak. [1913 Webster]
2. Of or pertaining to the early part of life; suitable to early life; as, youthful days; youthful sports. Milton. [1913 Webster]
3. Fresh; vigorous, as in youth. [1913 Webster]
"After millions of millions of ages . . . still youthful and flourishing." [1913 Webster]
youthful, adj.
1 young, esp. in appearance or manner.
2 having the characteristics of youth (youthful impatience).
3 having the freshness or vigour of youth (a youthful complexion).
Derivative:
youthfully adv. youthfulness n.
N youth, juvenility, juvenescence, juniority, infancy, babyhood, childhood, boyhood, girlhood, youthhood, incunabula, 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, young, youthful, juvenile, green, callow, budding, sappy, puisne, beardless, under age, in one's teens, in statu pupillari, younger, junior, hebetic, unfledged, youth on the prow and pleasure at the helm, youth a the glad season of life.