What is a fortified wine?

A fortified wine is defined as a wine to which extra alcohol has been added, typically in the form of distilled spirits such as brandy. This process raises the overall alcohol content of the wine and can also stop fermentation, preserving some of the natural sugars, which results in a sweeter flavor profile in some types of fortified wines.

This technique has a long history, particularly in regions such as Porto in Portugal, where fortified wines like Port are produced. The addition of alcohol can also help to stabilize the wine for aging and transport, making fortified wines robust and suitable for longer storage.

The other answer choices, while they describe certain types of wines, do not encapsulate the definition of fortified wine. Fermentation with high sugar levels (the first choice) may occur in grape juice leading to higher alcohol content, but it does not involve the addition of spirits. Long aging in oak barrels (the third choice) refers to maturation processes that can affect a wine's flavors and complexity but does not necessarily define it as fortified. Finally, making wine from dried grapes (the fourth choice) refers to processes like appassimento used in sweet wines, which is distinct from the definition of fortified wines.