pine vs knotty pine

pine and knotty pine both are nouns.

Word	Noun	Adjective	Verb	Adverb
pine	Yes	No	Yes	No
knotty pine	Yes	No	No	No

As nouns, knotty pine is a hyponym of pine; that is, knotty pine is a word with a more specific, narrower meaning than pine:

pine: straight-grained durable and often resinous white to yellowish timber of any of numerous trees of the genus Pinus
knotty pine: pine lumber with many knots; used especially for paneling and furniture

Other hyponyms of pine include white pine, yellow pine.

pine (noun)	knotty pine (noun)
a coniferous tree	pine lumber with many knots; used especially for paneling and furniture
straight-grained durable and often resinous white to yellowish timber of any of numerous trees of the genus Pinus

pine (verb)	knotty pine (verb)
have a desire for something or someone who is not present