Rice is not, as most readers know, simply rice. Good sake is made from proper sake rice, and cheaper sake is made from much less expensive rice. In fact, most run-of-the-mill sake is made with rice bought from the local agricultural co-op, and often the purchaser knows nothing about it other than it came from within that prefecture.
Among the 50 or so types of officially designated sakamai (sake rice), there are many differences that make each type more (or less) suited to sake brewing: size, starch content and the hardness of the grain are but a few of those considerations.
And even within one sakamai type, there are greater and lesser manifestations. Let's look at some of these differences, as well as how they are measured and conveyed.