Herbs, annual or perennial [or subshrubs to shrubs], erect, prostrate, creeping to ascending. Stems 4-angular or winged or terete, occasionally highly reduced. Stipules absent. Leaves simple, opposite; leaf blade margin serrate or entire or variously toothed. Inflorescences a terminal [or axillary] spike [or a terminal raceme or a cyme] or flowers solitary and axillary. Flowers perfect, with [or without] a bract and a bracteole. Calyx connate, 5-lobed or dentate; lobes usually less than 1/3 of calyx length. Corolla connate, tubular or cylindric, 2-lipped; lower lip with 3 imbricate lobes; upper lip 2-lobed. Stamens [2 or]4, inserted in corolla tube or exserted, anterior 2 longer; anthers longitudinally dehiscent. Gynoecium of 2 connate carpels; ovary superior, 1- or 2-locular; stigma broadly 2-lobed to 2-lipped, receptive only on inner surface and close together upon contact. Fruit an achene (in Phryma), loculicidal capsule (e.g., in Mimulus Linnaeus) [or occasionally berrylike (in Leucocarpus D. Don)]. Seeds numerous, rarely to 1, with an oblong embryo; endosperm scanty.