oyster mushroom vs oyster fungus

oyster mushroom and oyster fungus both are nouns.

Word	Noun	Adjective	Verb	Adverb
oyster mushroom	Yes	No	No	No
oyster fungus	Yes	No	No	No

As nouns, oyster mushroom and oyster fungus are synonyms defined as:

oyster mushroom and oyster fungus: edible agaric with a soft greyish cap growing in shelving masses on dead wood

Other synonyms of oyster mushroom include oyster agaric, Pleurotus ostreatus.

oyster mushroom (noun)	oyster fungus (noun)
edible agaric with a soft greyish cap growing in shelving masses on dead wood	edible agaric with a soft greyish cap growing in shelving masses on dead wood