episperm vs seed coat

episperm and seed coat both are nouns.

Word	Noun	Adjective	Verb	Adverb
episperm	Yes	No	No	No
seed coat	Yes	No	No	No

As nouns, episperm and seed coat are synonyms defined as:

episperm and seed coat: protective outer layer of seeds of flowering plants

Other synonyms of episperm include testa.

episperm (noun)	seed coat (noun)
protective outer layer of seeds of flowering plants	protective outer layer of seeds of flowering plants