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Graph (mathematics)




In Mathematics and Computer Science , a graph is the basic object of study in Graph Theory . Informally speaking, a graph is a set of objects called ''points'', ''nodes'', or ''vertices'' connected by links called ''lines'' or ''edges''. In a proper graph, which is by default ''undirected'', a line from point ''A'' to point ''B'' is considered to be the same thing as a line from point ''B'' to point ''A''. In a ''digraph'', short for ''directed graph'', the two directions are counted as being distinct ''arcs'' or ''directed edges''. Typically, a graph is depicted in diagrammatic form as a set of dots (for the points, vertices, or nodes), joined by curves (for the lines or edges).


DEFINITIONS


Definitions in graph theory vary. The following are some of the more basic ways of defining graphs and related structures.


Graph


A graph or '''undirected graph''' G is an Ordered Pair G := (V, E) that is subject to the following conditions:
  • V is a Set , whose elements are called vertices or '''nodes''',

  • E is a set of pairs (unordered) of distinct vertices, called edges or '''lines'''.


The vertices belonging to an edge are called the ends, '''endpoints''', or '''end vertices''' of the edge.