Kinematics: Joints

In 3D space two objects have 6 DoF (3 position coordinates, 3 angles) with respect to one another.

If they are (mechanically) connected, so that there are fewer DoFs -- then this is called a  "joint."

There are 6 types of "lower (order) mechanical joints":
H (helical),   R (rotational),   P (prismatic),   C (cylindrical),   S (spherical),   E (Ebene = plane).

There are also more complex, higher (order) joints -- but we ignore those in CS 184 (You may see them in CS 285).