The U.S. government security sold at a discount and maturing in one year or less is a Treasury bill.
Treasury bills, commonly called T-bills, are short-term debt obligations issued by the United States Department of the Treasury. They generally do not pay periodic coupon interest. Instead, investors buy them for less than their face value and receive the face value at maturity; the difference represents the investor's return.
U.S. Treasury bills are issued in several standard maturities, including 4, 8, 13, 17, 26, and 52 weeks, although the Treasury's offerings can change. Because their principal and interest are backed by the U.S. government, they are often treated as having very low credit risk, though their market value and real purchasing power can still be affected by interest rates and inflation.
T-bills differ from Treasury notes and bonds, which have longer maturities and generally pay coupons. A bill's discount price should not be confused with a discount on a company share.