This part provides a comprehensive account of the main theorems and mechanisms developed in the literature concerning friction-induced noise and vibration. Some of these mechanisms are based on experimental investigations for classical models. Bilinear and nonlinear dynamical models have been considered to explain such friction phenomena as stick-slip, chatter, squeal, and chaos. Nonlinear modeling includes two types of nonlinearities which differ from those encountered in structural dynamics. These nonlinearities, in addition to the observed uncertainty of friction between sliding surfaces, form a formidable difficulty in developing accurate and reliable modeling. They include the inherent nonlinearity of contact forces (eg, Hertzian contact), and the nonlinear relationship between friction and sliding relative velocity. Research activities in this area are a mixture of theoretical, numerical, and experimental investigations. Theoretical investigations are prevailed by deterministic analysis with few attempts of stochastic treatment. The models include classical and practical engineering models such as the mass-spring model sliding on a running belt or on a surface with Hertzian contact, a pin sliding on a rotating disk, beams with friction boundaries, turbine blades, water-lubricated bearings, wheel-rail systems, disc brake systems and machine cutting tools. There is a strong need for further research to promote our understanding of the various friction mechanisms and to provide designers of sliding components with better guidelines to minimize the deteriorating effects of friction.