Agaric and Oyster mushroom

Agaric noun - A saprophytic fungus of the order Agaricales having an umbrellalike cap with gills on the underside.

Oyster mushroom and agaric are semantically related. In some cases you can replace phrase "Oyster mushroom" with "Agaric", this terms are similar.

Oyster mushroom noun - Edible agaric with a soft greyish cap growing in shelving masses on dead wood.

Agaric and oyster mushroom are semantically related. Sometimes you can use "Agaric" instead a noun phrase "Oyster mushroom".