knock vs knock out

knock is a noun but knock out is not a noun.

Word	Noun	Adjective	Verb	Adverb
knock	Yes	No	Yes	No
knock out	No	No	Yes	No

knock (noun)	knock out (noun)
the act of hitting vigorously
negative criticism
a vigorous blow
the sound of knocking (as on a door or in an engine or bearing)
a bad experience

knock (verb)	knock out (verb)
find fault with; express criticism of; point out real or perceived flaws	destroy or break forcefully
knock against with force or violence	eliminate
rap with the knuckles	empty (as of tobacco) by knocking out
deliver a sharp blow or push	knock unconscious or senseless
make light, repeated taps on a surface	overwhelm with admiration
sound like a car engine that is firing too early