Parametrized post-Newtonian formalism
= Parametrized post-Newtonian formalism
{title2=PPN}
The <parametrized post-Newtonian formalism> expresses a weak-field <metric tensor> using phenomenological parameters so that different gravitational theories can be compared with the same observations. Its spatial-curvature parameter $\gamma_{\rm PPN}$ is one in <general relativity>; it is distinct from the kinematic <Lorentz factor>.