Flatfish and Righteye flounder

Flatfish noun - Any of several families of fishes having flattened bodies that swim along the sea floor on one side of the body with both eyes on the upper side.

Righteye flounder and flatfish are semantically related. In some cases you can replace phrase "Righteye flounder" with "Flatfish", this terms are similar.

Righteye flounder noun - Flounders with both eyes on the right side of the head.

Flatfish and righteye flounder are semantically related. You can use "Flatfish" instead a noun phrase "Righteye flounder".