Learn in the textbookBasics of Graph Theory
DefinitionAn edge (辺) is a line that joins two vertices and shows that a connection or relationship exists between them.
ExplanationAn edge always has a vertex at each end, and which two vertices it joins determines the relationship. An edge can carry a value such as distance, time, or cost, and this value is called a weight. With weighted edges, you can compare routes from one place to another by adding up the values on the edges.
AnalogyThink of the roads between towns. A road connects two towns, and if you write the travel time on each road, you can tell whether a route is a detour.
Memory hookThe kanji 辺 is the one used for a side of a triangle; remember it as the line joining one corner (vertex) to another.