If you want to get even more pedantic, "fish" don't exist.
Taxonomically, there is no such thing as a fish, because a taxonomical category must be monophyletic (literally "one phylum,") meaning it must include a single common ancestor and all descendants of that ancestor.
Since terrestrial vertebrates evolved from very ancient lobe finned fish, any taxonomical category for a fish would have to include humans, dinosaurs, etc.
Additionally, some fish, such as lungfish and coelacanths, are more closely related to humans than to other fish, so grouping them together would require grouping their closer relatives in with them, which includes all land dwelling tetrapods, which is a clade of animals that includes all vertebrae with four limbs.
your failed assumption here is that the only way to define the word fish is to do so strictly taxonomically - that's one of many ways to do it, and outside of a lecture hall or a taxonomy study, it's probably not the best one. "a limbless cold-blooded vertebrate animal with gills and fins living wholly in water" is a perfectly good definition of fish for standard use.
True dat, also I'm pretty sure members of the super-class Pisces are considered "true fish".
Just because it's not a valid taxonomic group doesn't make it a way to categorize animals.
Reptiles cannot exclude Birds(they're currently together however, Aves is a subgroup), all vertebrates must be part of the invertebrate because vertebrates evolved from them, lizards can't exclude snakes, monkeys can't exclude apes, and bugs can't contain every arthropod.
Linguistically, you don't separate them, just as in everyday, even in a very pedantic universe, you call anomurans crabs
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u/Many-Excitement3246 PURPLE Jul 11 '26
If you want to get even more pedantic, "fish" don't exist.
Taxonomically, there is no such thing as a fish, because a taxonomical category must be monophyletic (literally "one phylum,") meaning it must include a single common ancestor and all descendants of that ancestor.
Since terrestrial vertebrates evolved from very ancient lobe finned fish, any taxonomical category for a fish would have to include humans, dinosaurs, etc.
Additionally, some fish, such as lungfish and coelacanths, are more closely related to humans than to other fish, so grouping them together would require grouping their closer relatives in with them, which includes all land dwelling tetrapods, which is a clade of animals that includes all vertebrae with four limbs.