In the market

What it is: Cinnamon is a common name for the dried inner bark of evergreen trees in the genus Cinnamomum, native to tropical Asia. As the bark dries it curls into quills, which are either cut and sold as cinnamon sticks or ground into powder. There are several species of Cinnamomum grown for their bark, but the two most common are Ceylon or Sri Lankan cinnamon and Chinese or cassia cinnamon. In the United States, spice sellers are not required to make a distinction between the two, and because cassia cinnamon is more common and usually less expensive, that's what you're likely to get. Specialty spice shops usually stock both and tend to favor the Ceylon variety. Michael Heathers, co-owner of Portland Spice Company in Portland, Maine, says that Ceylon cinnamon has a lighter color and a stronger, sweeter, more floral, and rounder flavor than cassia. ''Ceylon cinnamon has a higher concentration of oil in the bark and that's where the flavor comes from," he says. Cassia cinnamon sticks are generally thicker and less brittle than Ceylon cinnamon sticks. They also cost about 50 cents to a dollar less per pound.

How to use it: As a background flavor, cinnamon can provide a warm sweetness and exotic depth to sweet and savory dishes. Classics like apple pie, Mexican hot chocolate, rice pudding, Indian curries, and Moroccan tagines would be lost without the sensual spice. Cinnamon sugar is a kid's favorite, particularly delicious on doughnuts or buttered toast.

What to look for: Like most spices, cinnamon begins to lose flavor and aroma as soon as it is ground. So if you want to keep it vibrant for years, look for whole quills and grind it yourself as you use it. If you buy powdered, keep it in an airtight container and in a cool, dark place, where it should be good for up to a year. When in doubt, use the smell test: If the ground cinnamon's aroma is faint, consider replacing it. -- JONATHAN LEVITT