A technique for the determination of the velocities of the parts of a machine or mechanism. Both graphical and analytical analyses of plane mechanisms will be discussed in this article, but of the several methods of each type available, only one of each type will be described. The graphical method will be discussed first, since the visualization which is an inherent part of the graphical analysis generally gives a better physical feel for the problem than most purely analytical methods. Analytical methods, however, are necessary for computer analyses.