a member at any level below a parent
descendant node of any node A is any node below A in a tree model, where "below" means "away from the root."
descendant node of any node A is any node below A in a tree model of a document, where "above" means "toward the root."
In a rooted tree, a descendant of vertex v is any vertex w whose path from the root contains v.
An object that appears in another object's group tree at any position below that other object. Every object is a descendant of its antecedents.