a small, hard seed, especially the seed of a food plant such as wheat, corn, rye, oats, rice, or millet.
the gathered seed of food plants, especially of cereal plants.
such plants collectively.
any small, hard particle, as of sand, gold, pepper, or gunpowder.
the smallest unit of weight in most systems, originally determined by the weight of a plump grain of wheat. In the U.S. and British systems, as in avoirdupois, troy, and apothecaries' weights, the grain is identical. In an avoirdupois ounce there are 437.5 grains; in the troy and apothecaries' ounces there are 480 grains (one grain equals 0.0648 gram).