What is meant by "residual sugar" in wine terminology?

Residual sugar in wine terminology refers specifically to the amount of sugar that remains in the wine after fermentation has taken place. During fermentation, yeast converts sugars present in the grape juice into alcohol and carbon dioxide. However, fermentation may not always convert all of the sugars into alcohol, leading to a certain level of sugar still present in the final product. This unfermented sugar is what is termed “residual sugar” and is a key factor in determining a wine's sweetness.

Wines with higher levels of residual sugar tend to be sweeter, while those with lower levels are drier. This concept is important for winemakers, as they can control the sweetness of the wine by stopping fermentation at a specific point, thereby allowing some of the natural sugars to remain in the finished wine. Understanding residual sugar is essential for pairing wines with food, making informed choices when buying wine, and appreciating the diverse styles of wine available.