Dessert wines tend to be much sweeter than other wines, so dessert wine glasses are generally shorter and hold less wine. Like other wine glasses, dessert wine glasses are designed especially to bring out the aromas and flavors of dessert wines. The glasses are smaller so that the drinker needs to tip his/her head back so that the sweetness doesn't overwhelm the mouth. Also, the small glass reflects the practice of generally drinking less dessert wine than dinner wines, as they are normally much higher in alcohol content. The small size of the wine glass also is because the sweetness of this after-dinner treat is supposed to close up the palate, and only small sips are necessary to complete this process.
Like other types of wine glasses, dessert wine glasses also feature a lip that's thinner at the top to allow for the correct type of drinking. They are also designed to allow for swirling of the wine to let the wine's aroma hit your nose as you drink. The ideal dessert wine glass is made of a thin, blown glass or a crystal so as to not interfere with the flavor of the wine. Most dessert wines are served either chilled or just below room temperature, so it's ideal that dessert wine glasses feature a stem so that the drinker's body heat doesn't warm the wine.
Some common types of dessert wines are port, sherry, Sauternes, and Moscato d'Asti . Often, sherry glasses are used for all types of dessert wines. Typically sherry glasses have a much smaller bowl, somewhere between 2 and 7 ounces, and they frequently flare at the top a bit to allow the aroma and bouquet of the dessert wine to be fully appreciated. Port glasses can vary slightly, but they generally also have a smaller bowl like the sherry glass and are frequently used for dessert wine. The definition of dessert wines and their preferred glassware varies slightly around the world, but you can expect to drink a dessert wine from a smaller glass.