Definition 37.7.3 (Centrally Orthogonal).label Let $H$ be a complex Hilbert space, $A \subset B(H)$ be a von Neumann algebra, and $\seqi{P}\subset \text{Proj}(A)$, then $\seqi{P}$ is centrally orthogonal if $\bracsn{Z(P_i)}_{i \in I}$ is mutually orthogonal.