Probability measure mathbbQ^T under which the T-maturity zero-coupon bond P(t,T) is the numeraire. Under mathbbQ^T, the forward rate F(t; T_1, T_2) for T_1 = T becomes a martingale, and any time-T payoff prices as V_0 = P(0,T),mathbbE^mathbbQ^T[payoff] — the discount factor pulls out of the expectation, making caplet and FRA pricing immediate.