Perennial or annual herbs or subshrubs; young stems and leaves often pubescent, but glabrous with age. Leaves opposite, entire. Inflorescences axillary or terminal, sessile or pedunculate, of various types. Flowers bisexual; tepals 5, outer 3 longer than and enclosing inner 2, glabrous inside; stamens (3)5, united below, anthers oblong or ovate, 2-locular, pseudostaminodia shorter or longer than stamens, subulate or ligulate, distally dentate to fimbriate; ovule 1, style obscure to slender, stigma capitate and globose to more or less punctate. Fruit an indehiscent utricle.