What documents issued by the Treasury Department that promise future repayment at a specific time or in intervals over time?

The documents issued by the Treasury Department that promise future repayment at a specific time or in intervals over time are known as Treasury securities. These include Treasury bills (T-bills), Treasury notes (T-notes), and Treasury bonds (T-bonds). T-bills are short-term securities that mature in one year or less, while T-notes have maturities ranging from two to ten years, and T-bonds are long-term securities with maturities of 20 or 30 years. All of these securities pay interest to investors, typically on a semiannual basis, and return the principal amount at maturity.