ricegrass vs cereal

ricegrass and cereal both are nouns.

Word	Noun	Adjective	Verb	Adverb
ricegrass	Yes	No	No	No
cereal	Yes	Yes	No	No

As nouns, cereal is a hypernym of ricegrass; that is, cereal is a word with a broader meaning than ricegrass:

ricegrass: any grass of the genus Oryzopsis
cereal: grass whose starchy grains are used as food: wheat, rice, rye, oats, maize, buckwheat, millet

Other hypernyms of ricegrass include cereal grass.

ricegrass (noun)	cereal (noun)
any grass of the genus Oryzopsis	a breakfast food prepared from grain
	foodstuff prepared from the starchy grains of cereal grasses
	grass whose starchy grains are used as food: wheat, rice, rye, oats, maize, buckwheat, millet

ricegrass (adjective)	cereal (adjective)
	made of grain or relating to grain or the plants that produce it