Much of what CXT wrote was correct. Having studied traditional Okinawan Karate for over 25 years, I have learned that most of the time the usage of "sho" and "dai" are parts of the same kata. "sho" in japanese means "small", "Dai" means "large". So the term "sho" is used to say this is a smaller version of the main kata. While "dai" is usually the full, or traditional, version of the kata. Beyond this, one shouldn't get too caught up in names though, because much of the differences in names are simply the difference between the Hogan dialect (Okinawan indigenous language) and the japanese version or translation. Like Pinan, or heian in japanese; Naihanchi, tekki in japanese; Wankan, Okan in Japanese; and many more...