joint has two degrees of freedom.
* A spherical joint, or ball joint, requires that a point in the moving body maintain contact with a point in the fixed body. This joint has three degrees of freedom.
* A planar joint requires that a plane in the moving body maintain contact with a plane in a fixed body. This joint has three degrees of freedom.
* A screw joint, or helical joint, has only one degree of freedom because the sliding and rotational motions are related by the helix angle of the thread.

Higher pairs: Generally,