Tree
Tree | WoodCoherent graph without cycles. A tree with n vertices always has n-1 edges. Between any two vertices of the tree there is a single route. Therefore, the tree is sometimes defined as the minimum coherence graph. Top of the tree which is connected to the rib with only one top, called the sheet.
oriented wood is a graph with a dedicated top (root), which between root and any top there is the only way.
Trees are used in various mathematical models: in the theory of formal systems, describing and designing hierarchical structures (in particular, in the information systems, including databases), scheduling, etc.