Which is true fish?

It's important to understand that "fish" is a broad term, and not all creatures that are called fish are truly fish in a scientific sense.

Here's a breakdown:

* True fish: These are aquatic vertebrates that belong to the class Pisces. They have gills for breathing underwater, fins for movement, and scales or bony plates for protection. Examples include:

* Salmon

* Tuna

* Goldfish

* Sharks

* Rays

* Not true fish: While these creatures may be called fish, they don't fit the scientific definition of being part of the class Pisces. Examples include:

* Jellyfish: They are actually cnidarians, a completely different group of animals.

* Starfish: They are echinoderms, a group of marine invertebrates.

* Crayfish: They are crustaceans, a type of arthropod.

* Sea Horses: They are true fish (class Pisces) but they are sometimes mistaken for something else due to their unique appearance.

So, to answer your question directly:

* True fish are those that belong to the class Pisces.

* Not true fish are creatures that may be commonly referred to as "fish" but belong to other animal groups.