This beverage is called sake in English, but in Japanese, sake or o-sake refers to alcoholic drinks in general. The Japanese term for this specific beverage is Nihonshu, meaning "Japanese sake."
Sake is also referred to in English as rice wine. However, unlike true wine, in which alcohol is produced by fermenting the sugar naturally present in fruit, sake is made through a brewing process more similar to that of beer. To make beer or sake, the sugar needed to produce alcohol must first be converted from starch. But the brewing process for sake differs from beer brewing as well, notably in that for beer, the conversion of starch to sugar and sugar to alcohol occurs in two discrete steps, but with sake they occur simultaneously. Additionally, alcohol content also differs between sake, wine, and beer. Wine generally contains 9-16% alcohol and most beer is 3-8%, whereas undiluted sake is 18-20% alcohol, although this is often lowered to around 15% by diluting the sake with water prior to bottling.
In general, it is best to keep sake refrigerated in a cool or dark room, as prolonged exposure to heat or direct light will lead to spoilage. Sake stored at room temperature is best consumed within a few months after purchase.
After opening the bottle of sake, it is best consumed within 2 or 3 hours. It is possible to store in the refrigerator, but it is recommended to finish the sake within 2 days. This is because once premium sake is opened, it begins to oxidize which affects the taste. If the sake is kept in the refrigerator for more than 3 days, it will lose its "best" flavour. However, this does not mean it should be disposed of if not consumed. Generally, sake can keep very well and still taste just fine after weeks in the fridge. How long a sake will remain drinkable depends on the actual product itself, and whether it is sealed with a wine vacuum top.