Plants annual or perennial; cespitose. Culms (1)4-140 cm, erect or geniculate at the lower nodes. Leaves cauline; auricles absent; ligules of hairs or membranous and long-ciliate; blades narrow, often involute. Inflorescences terminal, open or contracted (occasionally spikelike) simple panicles, exceeding the leaves. Spikelets laterally compressed, with 3-9 bisexual florets, reduced florets (if present) distal; disarticulation above the glumes and beneath the florets. Glumes subequal, exceeded by the florets, 1-veined; calluses short, bearded; lemmas 3-veined, 3-4-lobed or toothed, lateral veins pilose or ciliate, midveins glabrous or sparsely pubescent, all 3 veins extending into awns; paleas shorter than the lemmas, 2-veined; lodicules 2; anthers 3. Caryopses trigonous, falling free of the lemmas and paleas; embryos large relative to the caryopses. x = 10. Name from the Greek treis, three, and rhaphis, needle, alluding to the three awns of the lemma.