DOF refers to the six directions in which a component is free to move when it is first created or inserted into an assembly. These directions include three linear and three rotational as shown below. There are seven 3D constraints to choose from (Coincident, Tangent, Concentric, Parallel, Perpendicular, Angular and Gear). Each constrains a point, curve, edge, face or datum plane on the component to that of another component or parent object. A wide variety of constraint conditions can be created using these conditions and entity types. The parent object can be another component or the root part.