Annual or perennial, glandular, aromatic herbs. Leaves alternate, simple, entire or dissected. Flowers minute, bisexual and/or unisexual, usually mixed within inflorescence of axillary clusters, spikes or panicles; tepals 1–5, free or shortly united, sometimes hooded, inflated or spongy; stamens 1 or 2 rarely 5; styles 1–3; pericarp usually thinly membranous. Seed erect to horizontal, globular or laterally compressed.
About 32 species world-wide, mostly in tropical to warm-temperate regions; 18 species in Australia, 2 naturalised.