noun
infancy; very young age
Rare as a standalone modern noun for the period of infancy or early childhood; modern Japanese more often uses words such as 幼少期 or 幼いころ.
古い文章では、「幼稚」が幼い年ごろを表す名詞として出ることがある。
In older writing, 幼稚 can appear as a noun meaning a very young age.
na-adjective, noun
Common evaluative na-adjective for behavior, ideas, excuses, or arguments that seem childishly undeveloped; often critical.
そんな幼稚な言い訳は通用しない。
Such a childish excuse will not work.
彼の反論は感情的で、少し幼稚に聞こえた。
His objection was emotional and sounded a little immature.
na-adjective, noun
rudimentary; underdeveloped; primitive
Used for a method, theory, technology, or field that is still at an undeveloped or early stage; this is less about literal children and more about lack of sophistication.
当時の技術はまだ幼稚な段階にあった。
The technology at the time was still at a rudimentary stage.