oat vs cereal

oat and cereal both are nouns.

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

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

oat: seed of the annual grass Avena sativa (spoken of primarily in the plural as `oats')
cereal: foodstuff prepared from the starchy grains of cereal grasses

Other hypernyms of oat include food grain, grain.

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

oat: annual grass of Europe and North Africa; grains used as food and fodder (referred to primarily in the plural: `oats')
cereal: grass whose starchy grains are used as food: wheat, rice, rye, oats, maize, buckwheat, millet

Other hypernyms of oat include cereal grass.

oat (noun)	cereal (noun)
seed of the annual grass Avena sativa (spoken of primarily in the plural as `oats')	a breakfast food prepared from grain
annual grass of Europe and North Africa; grains used as food and fodder (referred to primarily in the plural: `oats')	foodstuff prepared from the starchy grains of cereal grasses
	grass whose starchy grains are used as food: wheat, rice, rye, oats, maize, buckwheat, millet

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