A fish is one fish and fish fish is two fish.
Yes, but under current law in most states they cannot get married.
The question does not make sense. The correct grammar is "a fish" not "an fish."
I prefer fish as the plural form, but fishes is also used.
Starfish are aquatic invertebrates but are oftenly called "Echinodermata" or the class Asteroidea. Happyanswers56: Starfish are aquatic invertabrates. so it's right.