Size of Graph/Examples/Arbitrary Order 4

Example of Size of Graph
Let $G = \struct {V, E}$ be the graph defined as:
 * $V = \set {v_1, v_2, v_3, v_4}$.
 * $E = \set {\set {\tuple {v_1, v_2}, \tuple {v_2, v_1} }, \set {\tuple {v_1, v_3}, \tuple {v_3, v_1} }, \set {\tuple {v_2, v_3}, \tuple {v_3, v_2} }, \set {\tuple {v_3, v_4}, \tuple {v_4, v_3} } }$

Then the size of $G$ is the cardinality of $E$:
 * $\card E = 4$