Sage
Wise Person
noun
A wise person is a sage! Or you can just be straightforward and call them a wise person.
賢人 is a somewhat old-fashioned word used to describe someone with deep knowledge or good judgment. It has a dignified, antiquated feel that makes you think of wise figures in old legends or classical literature.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
あの教授、外では賢人って言われてるけど、実は内弁慶らしいぜ。
That professor is called a sage outside the home, but I heard he's actually a braggart at home.