Higher pair:

 A higher pair is a kinematic pair wherein connection among two elements is just a point or line contact. The cam and follower arrangement illustrated in following figure is an instance of this pair. The contact among cam and flat faced follower is through a line. Other instance is ball bearings, roller bearings, gears, etc. A cylinder rolling on a flat surface contains a line contact when a spherical ball moving on a flat surface contains a point contact.

 Higher Pair