Graph Properties / Features

7. The two vertices connected by an edge are called the endpoints of the edge.
   

   The endpoints of the edge $\{\color{red}{1}, \color{red}{4}\}$ are vertices $\color{red}{1}$ and $\color{red}{4}$. Miriam Briskman, CC BY-NC 4.0.

   \documentclass[border=1pt]{standalone}
   \usepackage{tikz}
   
   \tikzset{
   vertex/.style={draw, circle, very thick, minimum size=1cm},
   edge/.style={very thick}
   }
   
   \begin{document}
   
   \begin{tikzpicture}
   
   \node[vertex, red, dotted] (v1) at (0,0) {1};
   \node[vertex] (v2) at (3,0) {2};
   \node[vertex] (v3) at (-2,-2.5) {3};
   \node[vertex, red, dotted] (v4) at (2,-2.5) {4};
   \node[vertex] (v5) at (5,-2.5) {5};
   
   \draw[edge] (v1) -- (v2);
   \draw[edge] (v1) -- (v3);
   \draw[edge, red] (v1) -- (v4);
   \draw[edge] (v2) -- (v5);
   
   \end{tikzpicture}
   
   \end{document}