Name a characteristic of fortified wines.

Fortified wines are specifically defined by the process of adding distilled spirits, such as brandy, to the wine. This addition increases the overall alcohol content, typically elevating it to levels significantly higher than standard table wines. This method not only enhances the alcohol content but also influences the flavor and stability of the wine, allowing for a broader range of styles, from dry to sweet.

While it is true that some fortified wines can be sweet, not all are required to be, making the statement that they are "always sweet" inaccurate. Similarly, fortified wines generally do not have low alcohol levels, as their characteristic enhancement comes from the additional spirits. The timing of grape harvest, while important for many wine types, does not specifically define fortified wines; they can be made from grapes harvested at different times, depending on the style and the winemaker's intent. The defining characteristic remains the addition of distilled spirits.