New and Knew

New is an adjective and means the opposite of "old."

Knew is the past-tense form of the verb "to know."

I knew him when he was a new student at the school.

A gnu, or wildebeest, is a large African antelope.  Gnu is also the name of a computer operating system.

I saw a new animal today.  I knew it was a gnu because of the horns.