  The dusty plasma system (containing nonthermally distributed inertialess
electron species, warm inertial ion species, and positively charged stationary
dust species) is considered. The basic features of subsonic and supersonic
modified-ion-acoustic solitary and shock waves formed in such a dusty plasma
system have been investigated by the reductive perturbation method. It has been
shown that positively charged dust species play a new role in favor of the
formation of subsonic solitary and shock waves. On the other hand, the ion
fluid temperature (represented by the parameter $\sigma$) and the electron
nonthermal parameter (represented by $\alpha$) play new significant roles
against the formation of subsonic solitary and shock waves and give rise to the
formation of the supersonic solitary and shock waves after their ($\sigma$'s
and $\alpha$'s) certain values. It is also shown that after a certain value of
the nonthermal parameter $\alpha$, the subsonic as well as supersonic solitary
and shock waves are formed with negative potential. The important applications
of the results of this theoretical investigation in space and laboratory dusty
plasma systems are pinpointed.
