Sweetness is mainly the flavor of sugar present in the wine, although alcohol and glycerol can add a perception of sweetness too.

A dry wine has a sugar level below the threshold of perception (up to about  4 grams per liter). If the wine is basically dry in style, but there is a tiny amount of detectable sugar (typically about 5 to 9 grams of sugar per liter) the wine is described as “off-dry”. Many “dry” Alsace Gewurztraminers, Brut Champagnes and inexpensive New World “dry” reds and whites are really “off-dry”.