  We study the large $N_c$ behavior of couplings among light meson states with
different compositions in terms of quarks and gluons. We shortly review the
most common compositions of mesons, which are of interest for the understanding
of low-lying meson resonances, namely, the ordinary quark-antiquark states as
well as the non-ordinary, glueball, tetraquark, etc. We dedicate special
attention to Jaffe's generalization of the tetraquark with $N_c-1$ $q\bar{q}$
pairs, that is the only type of state we have identified, whose width does not
necessarily vanish with $N_c$, while it does decouple exponentially with $N_c$
from the $\pi\pi$ channel, so that is weakly coupled to the meson-meson system.
