* Legumes are plants bearing seeds in pods that split when ripe. Lentils, beans and peas are the dried seeds, or pulses.
* Grains are the edible seeds of various plants belonging to the grass family. Wheat, corn, rice and oats are the most familiar grains. Plant researchers debate whether such grains as farro are wheat species or just wheatlike grains.
* Couscous and fregola are commonly mistaken for grains. They are actually grain products, made from coarsely ground durum wheat that has been sprinkled with water and rolled or grated to form grainlike foods similar to pasta.
* Sources for these ingredients include health-food stores and specialty shops. Items are also available by mail order from Kalustyan's (212-685-3451).