Arrack is a distilled alcoholic drink typically produced in India, Sri Lanka and Southeast Asia, made from the fermented sap of coconut flowers or sugarcane, and also with grain or fruit depending upon the country of origin. It is sometimes spelled arak, or simply referred to as 'rack or 'rak. It is not to be confused with the anise-flavored distilled spirit called arak or araq. In many parts of India arrack is colloquially known as "desi daru".

In food processing, fermentation is the conversion of carbohydrates to alcohol or organic acids using microorganisms—yeasts or bacteria—under anaerobic (oxygen-free) conditions. Fermentation usually implies that the action of microorganisms is desired. The science of fermentation is known as zymology or zymurgy.