gardening knife vs knife

gardening knife and knife both are nouns.

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

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

gardening knife: Any knife used in gardening.
knife: edge tool used as a cutting instrument; has a pointed blade with a sharp edge and a handle

gardening knife (noun)	knife (noun)
Any knife used in gardening.	edge tool used as a cutting instrument; has a pointed blade with a sharp edge and a handle
	a weapon with a handle and blade with a sharp point
	any long thin projection that is transient

gardening knife (verb)	knife (verb)
	use a knife on