  We study the structure of dynamically generated bound states in the chiral
unitary approach. The compositeness of a bound state is defined through the
wavefunction renormalization constant in the nonrelativistic field theory. We
apply this argument to the chiral unitary approach and derive the relation
between compositeness of the bound state and the subtraction constant of the
loop integral. The compositeness condition is fairly compatible with the
natural renormalization scheme, previously introduced in a different context.
