Rai seeds in English are commonly known as mustard seeds.
Mustard seeds, sometimes specifically referred to as black mustard seeds (though other varieties exist), are used both as a spice and as the base ingredient for prepared mustard. When cooked in oil, they release their characteristic spicy and nutty flavor. They are frequently used in Indian cuisine to temper (tadka) dishes, adding flavor to vegetables, pickles, and lentils.
