Sake in the six classifications above is known collectively as "tokutei meishoshu," or "special designation sake," and can for all intents and purposes be considered "premium sake." It constitutes only about 20% of all sake produced. Sake in the top four boxes is collectively known as "ginjo-shu" and can be considered "super-premium sake." (Yes, normal ginjo-shu is one subclassificaiton of the overall grouping ginjo-shu. It is only mementarily confusing!) Ginjo-shu and its subclasses constitute only the top  6% of all sake produced, and represents the pinnacle of the brewers' craft. 

Futsuu-shu
 

Futsuu-shu is "normal sake," i.e. sake that does not qualify for one of the above three levels of classifications. It is the equivalent of "table wine" in the wine world, and makes up about 80% of all sake that is made. Sake like this is produced with copious amounts of pure distilled alcohol added to increase yields. Although a lot of futsuu-shu is cheap, nasty, and vile, there is plenty of sake in this group is perfectly and enjoyably drinkable. One should avoid collectively dismissing futsuu-shu as rotgut.

 While some cheaper sake in this group also has sugars and organic acids added to "improve" the flavor (better futsuu-shu does not), note that no sake at all has any preservatives added to it.

Note: There is much overlap between above classications.
There are very fragrant junmai-shu, mellow and subdued daiginjo, very complex honjozo-shu, and everything in between. The classifications are really of only moderate usefulness because of this. Your palate and preferences are really the only true way to judge quality!

* About added alcohol
Cheap sake has copious amounts of distilled alchohol added to it at the final stages to increase yields. In the premium grades of sake, those above futsuu-shu, the three classifications on the left side (junmai-shu, junmai ginjo-shu, junmai daiginjo-shu), i.e. anything with the word "junmai" in it, has been made with rice only; no distilled alcohol has been added at all. This is the original and tradional method of brewing sake.

However, sake on the right side of the chart (honjozo-shu, ginjo-shu, daiginjo-shu), has had a very small amount of alcohol added to it at the final stages of brewing. This is not to increase yields, but rather the use of alcohol in this very controlled manner helps, claim some brewers, to pull out more aromatic and flavorful compounds that are soluble in alcohol from the fermenting mash when the completed sake is pressed away from the unfermented solids. It is a perfectly valid way to make great sake; it is in the end just one more method.

** About Rice Polishing
In general, the more the rice used in brewing is milled before being used, the higher the grade of sake. In fact, this is the clearest definition of the ascending grades of sake. In short:

Junmai-shu and Honjozo-shu are made with rice that has been "polished" (as the industry puts it), or milled, to remove at least the outer 30% of the original size of the grains. This means that each grain of rice is only 70% or less of its original size. 

Junmai Ginjo-shu and Ginjo-shu are made with rice that has been "polished" (as the industry puts it), or milled, to remove at least the outer 40% of the original size of the grains. This means that each grain of rice is only 60% or less of its original size.

Junmai Daiginjo-shu and Daiginjo-shu are made with rice that has been "polished" (as the industry puts it), or milled, to remove at least the outer 50% of the original size of the grains. This means that each grain of rice is only 50% or less of its original size.

Note the emphasis on the point that the numbers expressed for each grade are minimums. Very often the rice is polished much, much more than the minimum requirement. For example, it is quite common to find daiginjo that is made with rice polshed to 35%, so that a full 65% of the outside of each grain has been milled away before brewing. That means they grind away almost two thirds of their raw materials before beginning to brew. (To see how they do this, and the machines they use, go here.)

Note they do not throw away the powder that is ground away, but rather sell it to makers of traditional confectionaries and crackers, and some of it goes to animal feed. So none is wasted, but it is not used in the brewing process.

What is this all about? Why mill the rice so much?
In proper sake rice (which is different from normal table rice), starches -  which is what eventually ferments - are concentrated  in the center of the grains of rice. Surrounding this, closer to the surface of the rice grains, are found fats and proteins and things that adversely affect fermentation and in general lead to off-flavors, strange and generally unwanted components to the profile.

By milling the rice further and further, more and more of these unwanted fats, protiens, and nasties can be ground away before fermentation begins. This leads to cleaner, more elegant and more refined sake. It also allows more lively aromatics to come about.

So, in general, the more you polish the rice, the higher the grade of sake. I emphasize in general because there are exceptions based on style, personal preference, and a plethora of other factors. It is possible to take this rice milling thing too far, and grind away all distinction and uniqueness as well.

Rice Milling - Seimaibuai Premium sake is brewed with special rice in which the starch component (the shinpaku or "white heart") is concentrated at the center of the grain, with proteins, fats, and amino acids located toward the outside. For more on special sake rice, please click here. MILLING. With increased milling, one can remove more of the fats, proteins, and amino acids that lead to unwanted flavors and aromas in the brewing process. Ginjo-shu (premium sake) has at least 40% or more milled away. Daiginjo (super premium sake) has at least 50% or more milled away. SAKE RICE - MILLING OR SEIMAIBUAI Seimaibuai = Degree rice is milled before brewing Yamada Nishiki Rice A top-grade sake rice Unmilled 45% Milled Away Seimaibuai = 55% Ginjo Grade 55% Milled Away Seimaibuai = 45% Daiginjo Grade

There is no need to go to the top to enjoy good sake.
There is plenty of immensely enjoyable sake not in the top of the top classifications. In fact, sometimes such sake has more presence, uniqueness, and appeal than super dooper hoity toity high priced daiginjo. Well, sometimes, anyway.

Sake is almost always fairly priced.
You generally get what you pay for with sake. Up to a reasonable limit, if you pay 25 % more for sake B then sake A, you can expect about a 25% increase in quality and enjoyment (assuming that the particular "quality" increase in that particular sake is what you are looking for and prefer!). There are exceptions: there is some sake that is a bit pricey due to its lofty reputation. There are also a few tremendous bargains out there. But for most sake,  those not extremely expensive or extremely cheap, you will see an increase in quality that for the most part parallells the increase in price.

Note, speculation by the market and the opinion of "experts and critics" does not affect at all the market price of sake in Japan. Which is nice.

The "-shu" suffix, by the way, simply means "sake," and is often dropped when discussing sake. Hence, Junmai-shu is sometimes called simply Junmai, Honjozo-shu is very often called Honjozo. Similarly, people speak of ginjo, junmai-ginjo, daiginjo and junmai daginjo.

For a more detailed, text-oriented, less visual version of this information, click here.