also: ほうがよい
expression, i-adjective (yoi/ii class)
had better; should
Used after a past-tense verb to give strong advice or a recommendation, often implying a negative consequence if not followed.
早く寝た方がいいよ。
You had better go to bed early.
傘を持って行った方がいいです。
You should take an umbrella.
expression, i-adjective (yoi/ii class)
had better not; should not
Used after a negative verb (ない-form) to advise against doing something; the negative form is often contracted to ～ない方がいい.
See also: した方がいい
あまり夜遅くまで起きていない方がいい。
You had better not stay up too late.
そんなことは言わない方がいいですよ。
You shouldn't say things like that.
Formal variant with よい instead of いい; often used in polite or written contexts.
A grammaticalized construction from 方 (ほう, 'side/direction') + が (subject marker) + いい/よい ('good'), literally 'the side of doing X is good'. The past-tense verb before 方がいい is a conventional pattern, not a true past meaning.