 The ancestors of a node \(X\) are all those nodes from which we can reach \(X\) by following the arrows going forwards. The parents of a node \(X\) are those for which we can do this in one step. The descendants of \(X\) are all which can be reached from \(X\) by following the arrows going forward. The children are those for which we can do this in one step. In the example, \(H\) is the parent (and ancestor) of both \(W\) and BT, which are its children (and descendants). There are no non-parent ancestors or non-children descendants.