Which dog is not a breed?

This is a bit of a trick question! Here's why:

* All dogs are the same species: All dogs are *Canis lupus familiaris*, meaning they are all members of the same species.

* Breeds are artificial categories: Dog breeds are created by humans through selective breeding. They're not natural groupings like species.

So, technically, every dog is a breed because they are all part of the *Canis lupus familiaris* species.

However, if you're thinking about common dog breeds, like Golden Retrievers or Poodles, then a "mixed breed" dog is not a specific recognized breed. Instead, it's a dog with ancestry from multiple recognized breeds.

Let me know if you'd like to know more about dog breeds! 😊