Lentils, like other legumes, are seeds that grow inside of pods. What distinguishes lentils from the thousands of other legumes such as peas, beans, and peanuts is their double-convex, lens-like shape. In fact, the word lens comes from the Latin word for lentil. Common brown lentils are the mainstay of traditional lentil soup because they tend to disintigrate when cooked and thicken the soup.
1 lb. = about 2-1/4 cups = about 5 cups cooked
You can substitute other lentils, though their texture and flavor will differ some. French green lentils can sub in salad and side dishes but red lentils, which also fall apart during cooking, are a better substitute in a soup.
You can find brown lentils (often just called lentils) in supermarkets near the dried beans and split peas.
Pick the lentils over for tiny stones or other debris and rinse well. Unlike dried beans, lentils don't to be soaked before cooking; they cook in about 30 to 45 minutes.
Stored airtight in a cool dry place, lentils will last at least a year.