All these animal names (goat / crab / fish / etc) have accepted meanings. They may not match specific genus, but that’s ok.
That’s not what I’m referring to. “Fish” has an accepted scientific meaning. The accepted scientific meaning for “goat” is the genus Capra; the accepted scientific meaning for “crab” is the infraorder Brachyura. Among phylogeneticists, a “fish” is a non-tetrapod vertebrate, which unlike the other two is paraphyletic but nevertheless creates a completely rigid definition. It’s not about “matching a specific genus”; it’s about being well-defined among scientists.
These all have strict definitions that don’t resort to “well, it looks like [thing], so toss it on the pile.” There literally is such a thing as a fish.
That’s not what I’m referring to. “Fish” has an accepted scientific meaning. The accepted scientific meaning for “goat” is the genus Capra; the accepted scientific meaning for “crab” is the infraorder Brachyura. Among phylogeneticists, a “fish” is a non-tetrapod vertebrate, which unlike the other two is paraphyletic but nevertheless creates a completely rigid definition. It’s not about “matching a specific genus”; it’s about being well-defined among scientists.
These all have strict definitions that don’t resort to “well, it looks like [thing], so toss it on the pile.” There literally is such a thing as a fish.