Tree · WebGlossary.info

In computer science, a widely used abstract data type that represents a hierarchical tree structure with a set of connected nodes. Each node in the tree can be connected to many children (depending on the type of tree), but must be connected to exactly one parent, except for the root node (which has no parent). These constraints mean there are no cycles or “loops” (no node can be its own ancestor), and also that each child can be treated like the root node of its own subtree, making recursion a useful technique for tree traversal. In contrast to linear data structures, many trees cannot be represented by relationships between neighboring nodes in a single straight line. ← Wikipedia
In graph theory, an undirected graph in which any two vertices are connected by exactly one path, or equivalently a connected acyclic undirected graph. The term “tree” was coined in 1857 by Arthur Cayley. ← Wikipedia