One such grouping divides mechanisms into planar, spherical, and spatial categories. All three groups have many things in common,the criterion which distinguishes the groups, however, is to be found in the characteristics of the motions of the links.

• 其中一种归类法是将机械原理分成平面、球面和空间三类。尽管这三类机构都有许多共同点,然而分类的区别却在于连杆运动的特性。