Fetching details from the dictionary...

very young; little
childish; immature
彼女は幼い頃から絵が好きだ。
She has loved painting since she was young.
彼の幼い考えに周囲は呆れてしまった。
Those around him were exasperated by his childish thinking.
兄が留学したとき、私はまだ幼かった。
When my older brother went to study abroad, I was still very young.