whitefish in the US seafood market traditionally refers to cod, haddock, pollack and similar species, even including sole, flounder and halibut.

tilapia are cichlids, and are not part of the old definition; not sure if the definition has changed

Tilapia certainly does not refer to any whitefish. If tilapia is not "a fish" then neither are salmon or tuna or probably a dozen other common names.

Tilapia certainly does refer to (almost) any whitefish. Over 100 different fish are called 'tilapia'. Because their flesh is white, and they cannot pass as a more valuable fish.

For comparison, there are 8 species of salmon. We eat maybe two of them.

Most of those 100 fish are not eaten at any great scale. If you ask someone for examples of whitefish, you're going to get answers like cod, haddock, pollock etc. None of which are tilapia. Tilapia arguably isn't even an example of whitefish.

> Over 100 different fish are called 'tilapia'

All of which are cichlids.

That's a long way away from "any whitefish".

"Whitefish" most commonly refers to cod and pollock, not tilapia.

And we eat every species of salmon, not just two.