Short for appellation controlee, part of the French system that classifies wines according to their geographical origin. Each AC has a set of rules defining the region of production, permitted grape varieties and yields, and sometimes alcohol and sugar levels. For some ACs, a tasting panel must approve wines before they are sold. The system provides a guarantee of authenticity for the consumer while protecting the producer from competition. See also 'Vin de Pays', 'VDQS', 'Vin de table'.