On 11 June 2021, ISDA published the 2021 ISDA Interest Rate Derivatives Definitions (the 2021 Definitions), which were intended to replace the 2006 ISDA Definitions as the standard ISDA definitional book for cleared and non-cleared interest rate derivatives. ISDA no longer supports the 2006 ISDA Definitions. ISDA implements revisions to the 2021 Definitions by publishing updated electronic versions of the 2021 Definitions, each of which has a publication date, and which can be easily compared against any prior version via the ISDA online library. The 2021 Definitions include a number of key changes to provisions from the 2006 ISDA Definitions, including to the Calculation Agent provisions, business day provisions, calculation of the fixed and floating amount provisions, fallback provisions, exercise of swaptions/optional early termination provisions and cash settlement provisions. Each of these key changes will be addressed below in the relevant sections. The 2021 Definitions also continue the use of matrices, which are explicitly referenced throughout the 2021 Definitions. ISDA has published multiple matrices (some of which are updated versions