A planar mechanism is one in which all particles describe plane curves in space and all these curves lie in parallel plances; i.e. the loci of all points are plane curves parallel to a single common plane.

• 在平面机构中,所有的点在空间描出的是平面曲线,并且所有这些曲线都在平行平面上,也就是说,所有点的轨迹都是与一个单一公共平面相平行的平面曲线。