Flatfish and Lefteye 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.

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

Lefteye flounder noun - Flatfishes with both eyes on the left side of the head.

Flatfish and lefteye flounder are semantically related. You can use "Flatfish" instead a noun phrase "Lefteye flounder".