[soulfuldog]

The reason for the use of shortened names is because of the way Amazon named their early Kindle models. They were generally just 'Kindle' and to differentiate between the different releases, people started doing things like using which generation of Kindle it was and subsequently the firmware to give them a model number. It's far from perfect, and there is some confusion as ixtab has explained.

The Kindle 4 (basic Kindle, non-touch screen), Kindle 5 (Kindle Touch) is a bit confusing because there were two different models released at the same time and then there are actually two versions of the basic non-touch Kindle. The first was silver (K4S) and the second black one (K4B) was released at the same time as the Kindle Paperwhite. It's important to differentiate between them as the quality of the screen is better on the newer K4B than it is on the K4S, although they both run the same firmware.