expression, noun
Refers to someone one knows personally, not necessarily a close friend. Often used in contrast with strangers or in contexts of mutual recognition.
See also: 知人 (ちじん)
彼は知る人ぞ知る名カメラマンだ。
He is a famous photographer known to those in the know.
知る人もいない街で暮らすのは寂しい。
Living in a town where you know no one is lonely.
expression, noun
Archaic use for a romantic partner. In modern Japanese, 恋人 or 愛人 are more common.
昔の文には、知る人を恋しく思う歌が多い。
In old writings, there are many poems longing for one's lover.