Know means to be aware, to be informed, to recognize, to understand, or to be acquainted with.
Mary did not know the answer to the question.
I know that guy!
Tell me what you know about horses.
No means the opposite of "yes."
No, you may not color your hair blue.
My answer is no.
No also means none or not one.
No good deed goes unpunished.
There were no fish in the lake.
Knew vs New
These two words are pronounced the same—and even share most of their letters—but have completely different meanings.
Knew is the simple past tense form of the verb to know, while new is an adjective meaning recent or young:
Here are knew and new used in a sentence to illustrate:
A long time ago, nobody knew that the Earth was round.
Quantum computing is a very new industry.