  We present fully nonlinear and exact cosmological perturbation equations in
the presence of multiple components of fluids and minimally coupled scalar
fields. We ignore the tensor-type perturbation. The equations are presented
without taking the temporal gauge condition in the Friedmann background with
general curvature and the cosmological constant. For each fluid component we
ignore the anisotropic stress. The multiple component nature, however,
introduces the anisotropic stress in the collective fluid quantities. We prove
the Newtonian limit of multiple fluids in the zero-shear gauge and the
uniform-expansion gauge conditions, present the Newtonian hydrodynamic
equations in the presence of general relativistic pressure in the zero-shear
gauge, and present the fully nonlinear equations and the third-order
perturbation equations of the nonrelativistic pressure fluids in the
CDM-comoving gauge.
