cereal vs foodstuff

cereal and foodstuff both are nouns.

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

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

Other hypernyms of cereal include food product.

cereal (noun)	foodstuff (noun)
a breakfast food prepared from grain	(usually plural) consumer goods sold by a grocer
foodstuff prepared from the starchy grains of cereal grasses	a substance that can be used or prepared for use as food
grass whose starchy grains are used as food: wheat, rice, rye, oats, maize, buckwheat, millet

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