What is a Breed?

Hi,
I'm interested in getting an understanding of what people understand a cat "breed" to be. I know that what makes a cat purebred is the papers that accompany it, tracing its ancestry. However, I've also noticed that a lot of people think their pound kitties are one breed or another (I think pound kitties are wonderful...no offense intended). So, I'm asking:
How do you understand breed? By color, by appearance, by personality, or by papers?

Thanks! :)

Burmilla, there is no way to know that your cat is a particular breed unless there are papers. Most pound kitties are not purebred, they just exhibit characteristics of a certain breed. Even though there are a few more natural breeds than what Spencer mentions - Angoras, Vans, and Maine Coons come to mind - most of today's breeds are merely selective reproduction of a desired trait in a mix-breed cat, or a selective reproduction of a mix-pure cross. In other words, most of today's breeds are "designer" breeds, or man-made. Once you know this, it then comes as no surprise that so many Heinz 57 cats strongly exhibit certain purebred traits. And of course, even if your cat came from a pound, it still may be purebred - they, also are lost, abandoned, and surrendered. But it's more likely your cat just looks like a certain purebred.

Also, alot of people get coloring confused with breed. Tabby, for instance, is a coat pattern - but many people think it is a breed.

But you are correct when you assert that the only definitive way to know if you have a certain breed is by the papers.