We say that chambers $D$ and $D^{\prime}$ are

**adjacent**

along a wall $\left(v\right)^{\perp}$ whenever the intersection $$D\cap D^{\prime}\cap(v)^{\perp}$$ contains a non-empty open subset of $(v)^{\perp}$.

We say that chambers $D$ and $D^{\prime}$ are

**adjacent**

along a wall $\left(v\right)^{\perp}$ whenever the intersection $$D\cap D^{\prime}\cap(v)^{\perp}$$ contains a non-empty open subset of $(v)^{\perp}$.