Urad, also referred to as urad dal, urd bean, urd, urid, black matpe bean, black gram, black lentil (not to be confused with the much smaller true black lentil (Lens culinaris)), or white lentil (Vigna mungo), is a bean grown in southern Asia. It is largely used to make dal from the whole or split, dehusked seeds. It, along with the mung bean, was placed in Phaseolus but has been transferred to Vigna. It was at one point considered to belong to the same species as the mung bean.
Black gram originated in India where it has been in cultivation from ancient times and is one of the most highly prized pulses of India. It has also been introduced to other tropical areas mainly by Indian immigrants.
It is an erect, sub-erect or trailing, densely hairy annual herb. The tap root produces a branched root system with smooth, rounded nodules. The pods are narrow, cylindrical and up to 6 cm long. The bean is boiled and eaten whole or after splitting into dal; prepared like this it has an unusual mucilaginous texture. Ground into flour or paste, it is also extensively used in culinary preparation like dosa, idli, vada, and papad. When used this way, the white lentils are usually used. The white lentils are called "ulundhu" (உளுந்து) in Tamil.
The product sold as "black lentil" is usually the whole urad bean or urad dal. The product sold as "white lentil" is the same lentil with the black skin removed.