If $G$ is a connected graph, then $G$ contains an Euler circuit if and only if every vertex has even degree (Misunderstanding of terminology).

Question

I believe that I must be misunderstanding some of the terminology here. To my understanding, the included image is a connected graph where $\{ v_1,e_1,v_2,e_2,v_3,e_3,v_1 \}$ is contained within $G,$ and a Euler Circuit. Yet, $v_4$ clearly has degree one, which is odd. This is in contradiction with the Theorem, I believe I'm simply misunderstanding a definition, but I can't conclude what it is.