Annual or perennial herbs, or woody in a few genera; stems terete, internodes hollow or solid; leaves alternate, 2-ranked, simple, and parallel-veined, with sheathing bases, the sheaths usually open, typically with a ligule at junction of sheath and blade; flowers (florets) bisexual or unisexual, subtended by bracts (a lemma and usually a palea), in spikelets usually subtended by a pair of bracts (glumes); fruit a caryopsis.