A cereal of the genus Hordeum, a member of the Gramineae or grass family of plants that also includes wheat, rye, oats, maize, rice, millet and sorghum. There are two varieties (2-row, 6-row) classified according to the number of rows of seeds on each of the heads of the plant.
When malted, barley is the cereal grain preferred for brewing because the seed is covered by a husk that protects the germ during malting and helps to filter the wort during lautering by forming a filter bed. The essential qualities for brewing barley are high starch content, sufficient diastatic power to transform the starch into sugar, and low protein content.