に気をつける【にきをつける】

The expression に気をつける means "to be careful of," "to watch out for," or "to pay attention to" something. It is used to warn someone about a potential danger or to remind them to be mindful of something. The particle に marks the thing one should be careful about, and きをつける気をつける literally means "to attach one's attention (to something)."

Basic usage

The thing to be careful about is marked with に. This can be a noun, a nominalized verb phrase, or a clause ending in こと or の.

Common patterns

～に気をつけて is used as a parting phrase or a piece of friendly advice:

～に気をつけなければならない or ～に気をつけないといけない express that one must be careful:

～ように気をつける

When expressing what action to be careful about (especially with verbs), ～ように気をつける is used. This pattern means "to make sure to…" or "to be careful to…":

Politeness

In polite speech, きをつける気をつける becomes きをつけます気をつけます, and the imperative request form きをつけてください気をつけてください is very common. In casual speech, きをつけて気をつけて alone is used as a friendly "take care" or "be careful."