nut grass vs sedge

nut grass and sedge both are nouns.

Word	Noun	Adjective	Verb	Adverb
nut grass	Yes	No	No	No
sedge	Yes	No	No	No

As nouns, sedge is a hypernym of nut grass; that is, sedge is a word with a broader meaning than nut grass:

nut grass: a widely distributed perennial sedge having small edible nutlike tubers
sedge: grasslike or rushlike plant growing in wet places having solid stems, narrow grasslike leaves and spikelets of inconspicuous flowers

nut grass (noun)	sedge (noun)
a widely distributed perennial sedge having small edible nutlike tubers	grasslike or rushlike plant growing in wet places having solid stems, narrow grasslike leaves and spikelets of inconspicuous flowers