For low frequencies Ω Ω ≪ ≪ 1 the breather can be seen as a coupled kink–antikink pair. Kinks and breathers can move along the chain without any dissipative energy loss. Furthermore, any collision between all the excitations of the SG equation result in only a phase shift. Thus kinks and breathers may be considered nonlinear quasi-particles of the SG model. For nearly integrable modifications of the SG equation such as the continuum approximation of the FK model kinks can be considered deformable quasi-particles, provided that discreetness effects are small.