American Viticultural Area (AVA): A delimited, geographical grapegrowing area that has officially been given appellation status by the Alcohol and Tobacco, Tax and Trade Bureau (TTB). Two examples of AVAs are Napa Valley and Sonoma Valley.
Viticultural Area: Defines a legal grape-growing area distinguished by geographical features, climate, soil, elevation, history and other definable boundaries. Rules vary widely from region to region, and change often. Just for one example, in the United States, a wine must be 85 percent from grapes grown within the viticultural area to carry the appellation name.