Fermentation

From Beeripedia the Beer Wiki

Fermentation in brewing typically refers to the conversion of sugar in the wort to alcohol and carbon dioxide using yeast under anaerobic conditions. A more general definition of fermentation is the chemical conversion of carbohydrates into alcohols or acids. When fermentation stops prior to complete conversion of sugar to alcohol, a stuck fermentation is said to have occurred.

Fermentation usually implies that the action of the microorganisms is desirable, and the process is used to produce alcoholic beverages such as beer, and cider.