Acetic Acid
All wines contain acetic acid, or vinegar, but usually the amount is quite small--from 0.03 percent to 0.06 percent--and not perceptible to smell or taste. Once table wines reach 0.07 percent or above, a sweet-sour vinegary smell and taste becomes evident. At low levels, acetic acid can enhance the character of a wine, but at higher levels (over 0.1 percent), it can become the dominant flavor and is considered a major flaw. A related substance, ethyl acetate, contributes a nail polish-like smell.

Barrel Fermentation
A winemaking technique of fermenting grape juice in small barrels, usually made of oak.

Balance
A well-balanced wine is a primary goal of the wine maker. Such a wine blends all of its components gracefully: the fruit, tannin, acid, and sugar. A wine's balance may only be realized after some aging.

Breathing
Allowing a wine to mix with the air. Aeration occurs by pouring the wine into a larger container, such as a decanter or large wineglass. Breathing can be beneficial for many red wines and also for some young white wines. Chemically, breathing enables oxygen to mix with the wine, which hastens the aging process. If a wine stands open for more than 12 hours, it will begin to turn to vinegar as the oxygen continues to work. Whether to let a wine breathe before serving depends on the wine. Contrary to popular belief, it is not always beneficial to let older wines breathe prior to drinking, as this can cause them to "turn" - or go bad - before dinner is over.

Cold Stabilization
A clarification technique in which a wine's temperature is lowered to 32° F, causing the tartrates and other insoluble solids to precipitate.

Filtering
The process of removing particles from wine after fermentation. Most wines unless otherwise labeled are filtered for both clarity and stability.

Fining
A technique for clarifying wine using agents such as bentonite (powdered clay), gelatin or egg whites, which combine with sediment particles and cause them to settle to the bottom, where they can be easily removed.

Finish
The key to judging a wine's quality is finish, also called aftertaste a measure of the taste or flavors that linger in the mouth after the wine is tasted. Great wines have rich, long, complex finishes.

Length
The amount of time the sensations of taste and aroma persist after swallowing. The longer the better.

Méthode Champenoise
A French term for an intricate and time-consuming method used to make bottle-fermented sparkling wine. All Appellation d'origine Contrôlée sparkling wines made in France, including champagne, must be made by this process. Many sparkling wines made outside France are produced this way also.

Oak
The most popular wood for constructing barrels. Oak imparts flavors and tannin to wines during the barrel aging process; home winemakers can also accomplish this by using oak chips or powder.