Herbs, shrubs and trees, rarely woody climbers; branches and twigs tetragonal, not prominently nodose or articulated. Leaves opposite, decussate, rarely whorled or alternate, exstipulate, simple, rarely compound. Inflorescence definite and centrifugal or indefinite and centripetal, spicate, racemiform or panicled to umbellate or a head, very rarely solitary and axillary. Flowers usually zygomorphic, bisexual, hypogynous. Calyx gamosepalous, mostly tubular or campanulate, (2-) 4 (-7)-lobed or toothed to subentire, persistent, sometimes enlarging and concealing the fruit. Corolla gamopetalous, often with as many lobes as the calyx and somewhat bilabiate, with unequal lobes above and tubular below. Stamens mostly 4 and didynamous, inserted on the corolla tube and alternating with the lobes; staminodes often present; anthers dithecous, mostly dehiscing longitudinally. Gynoecium 2 (4-5)-carpellary, syncarpous, somewhat 4-lobed and 2-4-loculed, with usually one ovule in each apparent cell on axile placentation; style simple, terminal. Fruits usually schizocarpic or drupaceous with ± hard endocarp, indehiscent or dehiscent into 1-2(-1O)-celled pyrenes; seeds I-few.