immature
/ˌɪməˈtjuə(r); ?@ -tuər; ˌɪmə`tʊr/ adj
1 not sensible in behaviour or in controlling one's feelings; less mature than one would expect （行为或控制感情）不成熟的, 不够老练的
He's very immature for his age. 就他的年龄来说, 他还很不成熟.
2 not (yet) fully developed or grown （尚）未充分成长的; 发育（尚）未完全的
immature plants 幼嫩的植物.