* 子供っぽい (kodomo-ppoi): This is the most common and straightforward translation. It literally means "child-like" and is generally neutral. It implies behavior or characteristics reminiscent of a child.
* 幼稚 (yōchi): This word means "immature" or "infantile." It carries a more negative connotation than `kodomo-ppoi`, suggesting a lack of maturity that is inappropriate for the person's age.
* 子供じみた (kodomo-jimita): Similar to `kodomo-ppoi`, but slightly stronger and can imply a negative aspect, like acting childishly in a way that's embarrassing or annoying.
* ガキっぽい (gaki-ppoi): This uses the word `gaki` (ガキ), which is a more informal and sometimes derogatory term for a child. Therefore, `gaki-ppoi` carries a stronger negative connotation, suggesting the person is acting like a brat or a troublesome child.
The best choice depends on the context. If you're simply describing someone who acts like a child in a cute or endearing way, `kodomo-ppoi` is a good option. If you want to express disapproval of immature behavior, `yōchi` or `kodomo-jimita` would be more appropriate. Avoid `gaki-ppoi` unless you specifically want to express contempt.