any exception to the standard trading unit of a security. For example, with minor exceptions a standard or roundlot of stock is 100 shares, so any amount other than 100 shares or multiples thereof would be an odd-lot. The commission rate on an odd-lot transaction usually includes an odd-lot differential, typically 1/8th of a point. Thus the commission rate on an odd-lot transaction is relatively higher than on a round-lot transaction.