hay vs fodder

hay and fodder both are nouns.

Word	Noun	Adjective	Verb	Adverb
hay	Yes	No	Yes	No
fodder	Yes	No	Yes	No

As nouns, fodder is a hypernym of hay; that is, fodder is a word with a broader meaning than hay:

hay: grass mowed and cured for use as fodder
fodder: coarse food (especially for livestock) composed of entire plants or the leaves and stalks of a cereal crop

hay (noun)	fodder (noun)
grass mowed and cured for use as fodder	coarse food (especially for livestock) composed of entire plants or the leaves and stalks of a cereal crop
	soldiers who are regarded as expendable in the face of artillery fire

hay (verb)	fodder (verb)
convert (plant material) into hay	give fodder (to domesticated animals)