BN-pair
= BN-pair
{c}
{wiki}
A BN-pair in a group $G$ consists of subgroups $B,N$ such that $G=\langle B,N\rangle$, $H=B\cap N$ is normal in $N$, and $W=N/H$ has distinguished involutory generators satisfying the Bruhat multiplication axioms. The quotient $W$ is its <Weyl group>.