Definition: Money market instruments
External debt - IMF
Money market instruments are debt securities that generally give the owner the unconditional right to receive a stated, fixed sum of money on a specified date. These instruments usually are traded, at a discount, in organized markets; the discount is dependent upon the interest rate and the time remaining to maturity. Included are such instruments as treasury bills, commercial and financial paper, banker’s acceptances, negotiable certificates of deposit (with original maturities of one year or less), and short-term notes issued under note issuance facilities.
International Monetary Fund (IMF), "External Debt Statistics: Guide for Compilers and Users; Appendix I. Specific Financial Instruments and Transactions: Classifications", Washington D.C., 2003