In the Newman–Penrose (NP) formalism of general relativity, Weyl scalars refer to a set of five complex scalars { Ψ Ψ 0 , Ψ Ψ 1 , Ψ Ψ 2 , Ψ Ψ 3 , Ψ Ψ 4 } which encode the ten independent components of the Weyl tensor of a four-dimensional spacetime.