childish
US /ˈtʃaɪl.dɪʃ/
UK /ˈtʃaɪl.dɪʃ/

1.
infantile, puerile
of, like, or appropriate to a child
:
•
She has a very childish handwriting.
Ha una calligrafia molto infantile.
•
His behavior was quite childish for his age.
Il suo comportamento era piuttosto infantile per la sua età.