benthos vs endopsammon

benthos and endopsammon both are nouns.

Word	Noun	Adjective	Verb	Adverb
benthos	Yes	No	No	No
endopsammon	Yes	No	No	No

As nouns, endopsammon is a hyponym of benthos; that is, endopsammon is a word with a more specific, narrower meaning than benthos:

benthos: organisms (plants and animals) that live at or near the bottom of a sea, lake, river or stream
endopsammon: The microscopic fauna of sand and mud.

Other hyponyms of benthos include marine benthos, epipsammon, epixylon, merobenthos, epipelon, microbenthos.

benthos (noun)	endopsammon (noun)
organisms (plants and animals) that live at or near the bottom of a sea, lake, river or stream	The microscopic fauna of sand and mud.
a region including the bottom of the sea and the littoral zones