<P> Chi - Rho on the roof of the Basilica of St. John Lateran, Rome . </P> <Li> <P> Chi - Rho and Alpha and Omega on a modern Catholic altar . </P> </Li> <P> Chi - Rho and Alpha and Omega on a modern Catholic altar . </P> <Li> <P> Chi - Rho on YMCA building, Over-the - Rhine, Cincinnati, Ohio . </P> </Li>

What does px mean in the catholic church