Market participants often rely on abbreviations and in the interest rate swap markets, there's no exception. Two common terms you'll hear are IRS and OIS. IRS stands for interest rate swap, which can have two distinct meanings in practice. Firstly, the general meaning is that IRS is often used broadly to refer to any kind of interest rate swap, including a variety of structures, whether they involve fixed for floating swaps, basis swaps, floating for floating or other variations. There is, however, a specific meaning where in some cases IRS refers specifically to a fixed for floating interest rate swap, where the floating leg is tied to a term rate like EURIBOR or Term SOFR. In this case, the floating leg is set in advance at the start of each period and paid in arrears at the end of the period. OIS or overnight index swap by contrast refers exclusively to the type of interest rate swap where the floating leg is based on a series of overnight rates. Instead of being set in advance, the floating leg in OIS resets in arrears using multiple overnight resets.