Plants usually perennial; herbaceous, usually cespitose, occasionally rhizomatous. Culms 10-150 cm, not woody, sometimes branched above the base; internodes usually pith-filled, sometimes hollow. Leaves sometimes predominantly basal, sometimes predominantly cauline; sheaths open; auricles lacking; ligules of hairs or very shortly membranous and long-ciliate, the 2 types generally indistinguishable. Inflorescences terminal, usually panicles, sometimes racemes, occasionally spikes; primary branches without axillary pulvini and usually appressed to ascending, or with axillary pulvini and ascending to strongly divergent or divaricate. Spikelets with 1 floret; rachillas not prolonged beyond the florets; disarticulation above the glumes. Glumes often longer than the florets, thin, usually 1-3-veined, acute to acuminate; florets terete or weakly laterally compressed; calluses well-developed, hirsute; lemmas fusiform, 3-veined, convolute, usually glabrous or scabridulous, usually enclosing the palea at maturity, usually with 3 terminal awns, lateral awns reduced or obsolete in some species, lemma apices sometimes narrowed to a straight or twisted beak below the awns; awns ascending to spreading, usually straight, bases sometimes twisted together into a column or the bases of the individual awns coiled, twisted, or otherwise contorted, occasionally disarticulating at maturity; paleas shorter than the lemmas, 2-veined, occasionally absent; anthers 1 or 3. Caryopses fusiform; hila linear. x = 11, 12. Name from the Latin arista, awn.