Discount factor ($D_t=\exp (-{\int }_0^t{r}_{s}ds)$)

A multiplicative factor converting a value into units of a chosen initial account. With the continuous-time bank account $B$, $D_t=1/B_t$; discounted traded asset prices are martingales under the corresponding equivalent martingale measure.

The rate determining how future monetary flows are weighted relative to present flows; continuous discounting uses $e^{-rt}$.