Childish
Immature
noun, な adjective
He who is both in his infancy and immature is probably childish and immature.
When used as an adjective, 幼稚 describes negative immaturity in someone's behavior, remarks, or ideas. However, in compounds like 幼稚園 (kindergarten), it simply refers to the early childhood stage without any negative tone.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
うちの夫、本当に幼稚なんだよね。
My husband is really immature.
お言葉を返すようですが、幼稚な考えを持っているのは、ご自身の方じゃないですか？
I don't mean to contradict you, but don't you think you are the one who has childish ideas?
うちの子は今、土曜日の朝にある日本語学校の幼稚部に通っています。
My child is now attending the kindergarten section of a Japanese language school on Saturday mornings.
どうして幼稚な喋り方をする日本人女性が多いのですか？
Why do so many Japanese girls speak like children?