plant material vs cork

plant material and cork both are nouns.

Word	Noun	Adjective	Verb	Adverb
plant material	Yes	No	No	No
cork	Yes	No	Yes	No

As nouns, cork is a hyponym of plant material; that is, cork is a word with a more specific, narrower meaning than plant material:

Other hyponyms of plant material include cutin, chaff, husk, shuck, stalk, straw, stubble, plant product, vegetable tallow, wood.

plant material (noun)	cork (noun)
material derived from plants	the plug in the mouth of a bottle (especially a wine bottle)
	a small float usually made of cork; attached to a fishing line
	outer bark of the cork oak; used for stoppers for bottles etc.
	(botany) outer tissue of bark; a protective layer of dead cells

plant material (verb)	cork (verb)
	stuff with cork
	close a bottle with a cork