Is there a difference between a “single vineyard” and a “vineyard designate” wine?

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Dear Dr. Vinny,
Is there a difference between a “single vineyard” and a “vineyard designate” wine? Or are they two terms for the same thing?
—Florencia, Argentina
Dear Florencia,
They are two terms for the same thing: a wine made from grapes that all came from one vineyard. Single-vineyard wines are not necessarily better, but they certainly indicate a confidence that the wine is at least distinctive.
Blending grapes from multiple vineyards gives a winemaker more tools to create a consistent style or make up for a weak vintage, but single-vineyard wines can be more transparent when it comes to observing vintage variation. Keep in mind that if a wine lists a vineyard on the label, U.S. law dictates that at least 95 percent of the grapes used to make it came from that site.
—Dr. Vinny