public knowledge vs knowledge

public knowledge and knowledge both are nouns.

Word	Noun	Adjective	Verb	Adverb
public knowledge	Yes	No	No	No
knowledge	Yes	No	No	No

As nouns, knowledge is a hypernym of public knowledge; that is, knowledge is a word with a broader meaning than public knowledge:

public knowledge: knowledge that is available to anyone
knowledge: the psychological result of perception and learning and reasoning

Other hypernyms of public knowledge include cognition, noesis.

public knowledge (noun)	knowledge (noun)
knowledge that is available to anyone	the psychological result of perception and learning and reasoning