Well, I can see your point. But every one of their releases also has a number. If you read, you'll see that Leopard is OS X 10.5. Tiger is 10.4, Panther was 10.3, Jaguar was 10.2, and Puma was 10.1. Oh, and 10.0 was Cheetah. The whole list can be found at http://applepedia.com/Apple_Product_Codenames