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inexperienced (in life experience); unsophisticated; green; wet behind the ears
inexperienced (in love); innocent; naive; simple
「初心」 has another reading with different meanings.
恋愛に関しては彼女はとても初心だ。
When it comes to romance she is very inexperienced.
彼は見た目と違って初心な青年だった。
Despite his looks he was actually an innocent young man.
初心な少年だと思った。
I thought he was a naive boy.