Definition: Concessionality level
External debt - IMF
A net present value calculation, measured at the time the loan is extended, that compares the outstanding nominal value of a debt and the future debt-service payments discounted at an interest rate applicable to the currency of the transaction, expressed as a percentage of the nominal value of the debt. The concessionality level of bilateral debt (or tied aid) is calculated in a similar manner, but instead of using the nominal value of the debt, the face value of the loan is used—that is, including both the disbursed and undisbursed amounts, and the difference is called the grant element.
International Monetary Fund (IMF), "External Debt Statistics: Guide for Compilers and Users; Appendix III. Glossary of External Debt Terms", Washington D.C., 2003