Perennial or rarely annual herbs, sometimes with a woody base. Leaves opposite on lower stems, often becoming alternate near inflorescences. Flowers usually actinomorphic, solitary in upper leaf axils; bracteoles absent; hypanthium usually short but evident, deciduous after anthesis; sepals 4, free, deciduous; petals 4, obovate to emarginate, usually white, pink or purplish, sometimes yellow or red (neither in Australia); stamens 8; ovary 4-celled. Fruit a many-seeded slender, elongate, loculicidal capsule; seeds more or less obovoid, usually crowned with a coma of long, fine hairs.
About 165 species, widespread throughout the world, particularly at high latitudes and high altitudes; 18 species in Australia, 16 native and 2 naturalised.