Find the odd number / letters / word from the given alternative.

Wheat
Barley
Rice
Pea E. Mustard

The odd one out is mustard. The other four are cereal crops, while mustard is a member of the mustard family, Brassicaceae. Cereal crops are grown primarily for their edible seeds, which are used to make flour, bread, pasta, and other foods. Mustard is grown for its seeds, which are used to make mustard, a condiment.