Vertex = Node = Point
A graph is a diagram consist of a set of points and a set of lines or arcs. Graph theory is equal to Graph story. It is a story about the points and arc.
In the beginning, in the family name Graph , there is a point. This point is called a vertex . It is an isolated point of Graph. It feels so lonely.
Teknomo, Kardi (2015) Pictorial Introduction to Graph Theory. http:\\people.revoledu.com\kardi\tutorial\GraphTheory\