Annual or perennial herbs sometimes prennating by stolons. Leaves mainly crowded in a basal rosette; cauline opposite below, ± alternate above. Inflorescence an often secund scapose terminal raceme. Bracts present. Calyx infundibular to campanulate, 5-fid, lobes ± equal. Corolla personate, tube very short; limb bilabiate. Upper lip erect, entire or shortly bifid, much smaller than lower lip; lower lip larger, spreading, 3-lobed; middle lobe of lower lip with 2 deep channels on under side and 2 ridges clothed with clavate glandular hais on upper side. Stamens 4, didynamous, inserted in corolla tube; anthers 2-celled, cells divergent. Fruit a loculicidal 2-valved capsule. Seeds very numerous, minute.

About 30 species, from Afghanisan eastwards and southwards through temperate and tropical Asia to Australasia and west central India; naturalized elsewhere. By far the greatest centre of diversity is China. Represented in Pakistan by three native species. 

In the APG III classification (2009) Mazus is included in the family Phyrmaceae.

Care should be taken in the field to make detailed notes about the following characters, which are lost or scarcely evident in most herbarium material but are very helpful to correct identification: colour of upper lip; colour of lower lip; colour of hairs on palate ridges.