  Interacting galaxies are a natural arena for studies of non-equilibrium
stellar dynamics, gas dynamics, and thermodynamics. Only galaxy formation
itself is as deeply concerned with as many different aspects of dynamics, and
the connection between interactions and the formation of galaxies is probably
no coincidence. This review discusses tidal interactions, halos and orbit
decay, dissipative effects in galaxy interactions, properties of merger
remnants, and origins of starbursts.
