Wine, simply, is a fermented beverage made from fruit, any fruit. If all the sugars are fermented, it's a "dry wine". That is all that dry means, very low residual sugar levels. Sweet wines are produced by interrupting fermentation to retain some sugar. With port, they add alcohol to stop fermentation, for example. Blackberry wine is wine, they usually leave it sweet. Sake is not wine, it's more akin to beer, because neither use fruit for fermentation.