premature and puerile, petty
juvenile
undeveloped, immature, early, unready, unripe
immature
Here are 4 words to get you started: unready, unripened, green, or immature
People were talking about how immature the boy was.
"Immature" is an adjective, the opposite of "mature."
Careless and reckless are synonyms for irresponsible. Immature is another synonym.
ish.---Actually, -ish is a suffix, not a prefix. A prefix is the front part of a word. For instance, take the word immature. That means childish, and the prefix is im- which means not. So an immature person is not mature, but childish.If you want another suffix for child that makes the meaning the same, you can add -like. So a person can be childlike.
Immature can mean childish or stubborn. The immature boy did not want to tie his shoes, and then fell.
immature
You are immature.
She ended the relationship because he was too immature.Your immature actions resulted in your ban.The thought was a rather immature one.
imago