Any of several BRASSICA species that are commonly called mustard. Brassica juncea is brown or Chinese mustard, and Brassica nigra is black, brown, or red mustard. The plant is grown both for mustard seed from which oil is extracted or used as SPICES, and for its greens used as VEGETABLES or ANIMAL FEED. There is no relationship to MUSTARD COMPOUNDS. A species from a related genus SINAPIS ALBA is white mustard.