tree structure

A tree structure is a way of representing the hierarchical nature of a structure in a graphical form. It is named a "tree structure" because the graph looks a bit like a tree, even though the tree is generally shown upside down compared with a real tree; that is to say with the root at the top and the leaves at the bottom.
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A hierarchical organization in which a given node is considered to be an ancestor of all the lower level nodes to which the given node is connected. Note 1: The root node, i.e., the base node, is an ancestor of all the other nodes. Note 2: In a tree structure there is one and only one path from any point to any other point.