benthos vs epixylon

benthos and epixylon both are nouns.

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

As nouns, epixylon is a hyponym of benthos; that is, epixylon 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
epixylon: organisms that are attached to submerged wood surfaces in aquatic ecosystems.

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

benthos (noun)	epixylon (noun)
organisms (plants and animals) that live at or near the bottom of a sea, lake, river or stream	organisms that are attached to submerged wood surfaces in aquatic ecosystems.
a region including the bottom of the sea and the littoral zones