food grain vs cereal

food grain and cereal both are nouns.

Word	Noun	Adjective	Verb	Adverb
food grain	Yes	No	No	No
cereal	Yes	Yes	No	No

As nouns, food grain and cereal are synonyms defined as:

food grain and cereal: foodstuff prepared from the starchy grains of cereal grasses

Other synonyms of food grain include grain.

food grain (noun)	cereal (noun)
foodstuff prepared from the starchy grains of cereal grasses	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

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