knife vs weapon

knife and weapon both are nouns.

Word	Noun	Adjective	Verb	Adverb
knife	Yes	No	Yes	No
weapon	Yes	No	No	No

As nouns, weapon is a hypernym of knife; that is, weapon is a word with a broader meaning than knife:

Other hypernyms of knife include arm, weapon system.

knife (noun)	weapon (noun)
edge tool used as a cutting instrument; has a pointed blade with a sharp edge and a handle	any instrument or instrumentality used in fighting or hunting
a weapon with a handle and blade with a sharp point	a means of persuading or arguing
any long thin projection that is transient

knife (verb)	weapon (verb)
use a knife on