# What is a central projection?

What is a central projection in the context of a C*-algebra or a W*-algebra? Unfortunately while I see results on this concept, I haven't been able to find a definition.

Thanks!

It is just a projection that is central (i.e., in the center). That is, a central projection in a *-algebra $A$ is an element $p\in A$ such that $p=p^*$, $p^2=p$, and $px=xp$ for all $x\in A$.