Annual or perennial herbs, shrubs or subshrubs, sometimes scandent, rarely small trees, with opposite leaves and branches; leaves simple, entire or ± incised. Flowers hermaphrodite, polygamous or dioecious, bibracteolate, in axillary and terminal bracteate spikes, sometimes condensed to capitula or frequently paniculate; bracts and bracteoles small, membranous. Perianth segments 5, free, frequently pilose or lanate. Stamens 5, shortly monadelphous at the base, pseudo-staminodes occasionally well-developed, more commonly short or obsolete. Stigmas 2-3, elongate, or sometimes capitate in functionally male flowers. Ovary with a single pendulous ovule. Capsule membranous, indehiscent.