Annual, biennial or perennial herbs. Leaves opposite (in Australia), entire; stipules absent. Inflorescence cymose, or of 1–several dichasia, sometimes reduced to a single flower. Flowers regular, bisexual, 4–9-merous; calyx c. tubular to funnel-shaped, shallowly to deeply lobed; corolla rotate, cup-shaped, funnel-shaped, campanulate or tubular; stamens as many as and alternating with corolla-lobes, fused with corolla to some degree, anthers longitudinally dehiscent; nectary disc or discrete nectaries usually present; ovary superior, 1- or 2-locular, 2-carpellate; ovules numerous; style usually bifid (each arm sometimes again divided), often deciduous. Fruit a septicidal capsule; seeds numerous.
An almost cosmopolitan family of c. 80 genera and c. 920 species; 6 genera (2 naturalized) and c. 27 species in Australia.