Plants of the family Gramineae (Poaceae) which range from small, twisted, erect, or creeping annuals to perennials. Stems are called culms with well-defined nodes and internodes. Leaves arise alternately in two rows from the nodes. The leaf is composed of two parts, the leaf sheath which clasps the stem, the margins overlapping to form the tube, and the leaf blade which is usually thin, narrow, and linear with parallel venation; a large member among the monocotyledonous plants (monocots).