A truncated moment formalism for general relativistic radiation hydrodynamics, based on Thorne's moment formalism, is derived. The fluid rest frame is chosen to be the fiducial frame for defining the radiation moments. Then, zeroth-, first-, and second-rank radiation moments are defined from the distribution function with a physically reasonable assumption for it in the optically thin and thick limits. The source terms are written, focusing specifically on the neutrino transfer and neglecting higher harmonic angular dependence of the reaction angle. Finally, basic equations for a truncated moment formalism for general relativistic radiation hydrodynamics in a closed covariant form are derived assuming a closure relation among the radiation stress tensor, energy density, and energy flux, and a variable Eddington factor, which works well. We note that only electron neutrinos can be degenerate in general. For antielectron neutrinos, μ c < 0 and for muon and tau neutrinos, μ c = 0, when these neutrinos are in thermal equilibrium with matter. Thus, these are not degenerate in general.