Which term describes the sensation of bitterness in a wine?

The correct choice is related to the sensation of bitterness in wine, which is primarily attributed to tannins. Tannins are naturally occurring polyphenolic compounds found in grape skins, seeds, and stems, as well as in oak barrels used for aging wines. They contribute to the structure and astringency of wine and can create a dry, bitter sensation on the palate. This mouthfeel is often described as "grippy" or "astringent."

While acidity can contribute to the overall flavor profile of a wine, it primarily brings freshness and crispness rather than bitterness. Sweetness counteracts bitterness, providing balance in wines, and alcohol contributes warmth and can enhance the overall sensory experience but is not directly linked to bitterness. Tannins, therefore, are the primary factor in imparting a bitter sensation in red wines, making this the correct answer.