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The plants can exist as trees or can be reduced to mere shrubs or bushes with or without spines. The branches are often covered with hairs or trichomes. The leaves usually alternate, are decussate, vary in size, are simple and can be either sessile or petiolate. Amongst the Acanthaceae, the plants are astipulate. 

Moreover, cymose inflorescence is observed among members of this family. The axilliary flowers are grouped in bunches, in simple or compound racemes. They are usually hermaphroditic, habitually large, brightly coloured, zygomorphic, very rarely actinomorphic or sometimes accompanied by 2 or 3 to 4 bracteoles that form an involucre below the calyx. The calyx is highly variable with a maximum of 5 sepals that may be equal or unequal and the corolla is gamopetalous. 

The lamina is bilabiate with the upper lip having 2 lobes, while the lower one is trilobed. Four (4) anthers are borne on the filaments that can be free or fused together in a didynamous fashion. The style is cylindrical or filiform, while the stigma is divided into two equal lobes or two largely unequal lobes. On the other hand, the ovary is superior, bears two parallel or superimposed chambers. 

Axile placentation is observed amongst the anatropous ovules that bear hygroscopic trichomes. The seeds can be smooth, scaly or wart-like. The fruits exist in the form of bilocular capsules, but very rarely are these unilocular, indehiscent and in the form of drupes.