For instance, when a conveyance is made to a man, his assent to it is presumed, for the following reasons; cause there is a strong intendment of law, that it is for a person's benefit to take, and no man can be supposed to be unwilling to do that which is for his advantage. 2.
Informally, a graph is a finite set of dots called vertices (or nodes) connected by links called edges (or arcs). More formally: a simple graph is a (usually finite) set of vertices V and set of unordered pairs of distinct elements of V called edges. Not all graphs are simple.
A tree is a mathematical structure that can be viewed as either a graph or as a data structure. The two views are equivalent, since a tree data structure contains not only a set of elements, but also connections between elements, giving a tree graph. Trees were first studied by Cayley (1857). McKay maintains a database of trees up to 18 vertices, and Royle maintains one up to 20 vertices.