Annual to perennial herbs, sometimes subshrubs, usually glabrous, often fleshy. Leaves alternate or opposite and decussate and then sometimes connate, simple and entire; stipules scarious, bristle-like or absent. Flowers bisexual, actinomorphic, hypogynous or half-epigynous. Sepals usually 2, free or united below. Petals 2–6(–18), free or united below, sometimes minute or absent. Stamens (1–)3–20 or rarely more, opposite the petals when equalling them in number. Style simple or with two or more branches. Ovary superior or semi-inferior, usually 1-celled, with one to many ovules on a basal placenta. Fruit a capsule, opening by valves or transversely; seeds one to many, with a curved embryo surrounding the mealy perisperm.

Contains some 20 genera with about 500 species mainly in temperate and subtropical regions.