i-adjective
Used as an adjective meaning something is not known or recognized. Often used in the phrase 知らない人 (stranger).
この町は知らない場所ばかりだ。
This town is full of unfamiliar places.
知らない人から電話がかかってきた。
I got a call from an unknown person.
interjection
I don't care; whatever; that's irrelevant
Interjection expressing indifference or dismissal. Often used in casual speech to brush off a topic.
知らない!好きにすれば?
I don't care! Do whatever you want.
あの人のことはもう知らない。
I don't care about that person anymore.