The body of a wine refers to its mouthfeel, with light-bodied wines being less viscous that full-bodied wines. Remember, viscosity describes the thickness or texture of a liquid, with water being less viscous than syrup, for example.
Tannins is the other term that comes up a lot. Tannins are naturally occurring compounds called polyphenols. These are found in grape skins and give wines a noticeable dryness.
Light red wines generally have a lower alcohol content of less than 12.5 percent. They also have less tannins than medium- or full-bodied wines. Pinot Noir, Grenache, and Barbera are a few examples.
Medium-bodied red wines tend to have an alcohol content of between 12.5 and 13.5 percent and more tannins than a light-bodied red wine but less than a full-bodied red wine. Examples include Merlot, Shiraz, Tempranillo, and Nebbiolo.
Any red wine with more than 13.5 percent alcohol is considered a full-bodied wine. Full-bodied wines have more complex flavors and have a richer mouthfeel. Examples include Cabernet Sauvignon, Zinfandel, and Syrah.