  The 1/$N_c$ arguments are developed to classify the hadronic states in the
correlators. Arguments applied to the $\sigma$ meson correlator enable to
separate the instanton, glueball, and, in particular, the $\pi\pi$ scattering
states by $1/N_c$ from both 2q and 4q correlators. The bare resonance pole with
no mixing effects are analyzed with the QCD sum rules (QSR). The results
suggest the existence of nontrivial correlation for the mass reduction of 4q
system.
