Following other technology companies and in light of recent events the technical terminology of master/slave has been changed to main/secondary.

We now have:

Parent – ChildThis is a depends-on relation used to denote that a “child” node depends on a “parent” node.
In general the Child follows the Parent.

Parent-Child relations are shown in the node-tree
Points and axis (and rigid-bodies) can have a Parent node. This means that the are located ON that parent node.
Circles and Forces must have a parent (Point).
Geometric-Contacts have a parent_node and a child_node meaning that the child-node will be placed on the parent node.
Main – SecondaryThis is an unequal relationship of similar nodes.In the 6D linear connector the Main node is connected with the Secondary node via a set of springs. The stiffness of those springs and the relative displacements are defined in the axis system of the main node.
A – BThis is an equal relationship of similar nodes.For example linear beams, cables, 2D connectors have an A and an B end.
(for linear beams there is a small different between A and B as the beam leaves A in the X-direction and enters B in the X-direction)