18
green(adjective, healthy, experienced, immature)
15
immature(adjective, inexperienced, young)
12
young(adjective, old, immature)
9
childish(adjective, silly, immature)
9
youthful(adjective, new, old, immature)
8
jejune
6
juvenile(adjective, childish)
6
unripe(noun, adjective, reading, immature)
6
sentimental(hard, cool)
6
silly(adjective, foolish, absurd, giddy)
5
infantile(adjective, babyish)
5
babyish(adjective, like)
5
undeveloped(adjective, immature)
5
unfledged
4
inexperienced(adjective, old, immature, seasoned)
4
kiddish
4
unformed(adjective, developed)
3
puerile(adjective, childish)
3
adolescent
3
embryonic
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APASmart Define. (2015). mature thesaurus. Retrieved September 26, 2026, from https://smartdefine.org/mature/thesaurus/antonyms
ChicagoSmart Define. 2015. "mature thesaurus" https://smartdefine.org/mature/thesaurus/antonyms (accessed September 26, 2026).
HarvardSmart Define 2015, mature thesaurus, Smart Define, viewed 26 September, 2026, <https://smartdefine.org/mature/thesaurus/antonyms>.
MLASmart Define. "mature thesaurus" 10 April 2015. Web. 26 September 2026. <https://smartdefine.org/mature/thesaurus/antonyms>