A pair $(V,\Delta)$ is klt iff $K_{V}+\Delta$ is $\mathbb{Q}$-Cartier and if for any log-resolution $\pi:X\to V$ of $(V,\Delta)$, we have the numerical equivalence of Cartier divisors:

$$N(K_{X}+\Delta^{\prime})\cong\pi^{*}N(K_{V}+\Delta)+\sum_{E\ exc.}Na_{E}E$$

with $a_{E}>-1$, $\Delta^{\prime}$ the proper transform of $\Delta$ in $X$ (same multiplicities) and $N$ is an integer such that $N(K_{V}+\Delta)$ is Cartier.