A varietal is simply a single type of grape used in wine production.
A “varietal wine” is made predominantly from one type (or varietal) of grape.
Examples of varietals include Pinot Noir, Riesling, and Syrah.
In Oregon, a varietal wine must contain at least 90% of its wine from a single variety of grape. The other 10% may come from blending in other varietals, a practice commonly employed by wineries to produce unique flavors in their wines. This other 10% may also result from a vineyard whose vines containing a few “stray” varietals, which, unless expressly detected, may go unknown for years.
The only exception to Oregon’s 90/10 law is with Cabernet Sauvignon, which may contain up to 25% of another varietal.