Also known as residual sweetness (RS), the amount of sugar in the wine that is retained by a natural end of fermentation or by deliberate stopping. The latter can be achieved in various ways such as cooling or by adding sulphur or alcohol. The residual sugar consists mainly of fructose (fruit sugar), because the glucose (grape sugar) is converted faster into alcohol and carbon dioxide, and to a small extent of non-fermentable sugars(pentoses). The remaining sugar content (dry to sweet) can be optionally stated on the label, as regulated by wine law. The phenomenon that the subjective perception of sweetness in wine, especially at high acidity levels, can differ relatively strongly from the actual analytical values is described under sweet.