callow

adolescent, green, immature, inexperienced, juvenile, puerile, raw, unfledged, unformed, unripe, unripened

babyish, childish, infantile, infantilized, infantine; boyish, girlish, juvenescent, kiddish, young, youngish, youthful; maidenly, virginal; ingenuous, innocent, naive ( naïve), tender; unknowing, unseasoned, unsophisticated, untrained, untried

advanced, precocious; knowing, savvy, sophisticated, worldly, worldly-wise