Be a good kid.

Meaning: This means to behave in a way that is considered morally right or virtuous.

Choice of Words: Be means to exist or to have a particular quality or characteristic. Good means morally right or virtuous. Kid is a young person, especially a child. When you put them together, "Be a good kid" is a request for a child to behave in a way that is considered morally right or virtuous.

Alternative Expressions

Related Expressions