A multigraph can contain a multiple edge between the same two vertices.
多重图可以在同一对顶点之间包含重边(平行边)。
When modeling airline routes, using multiple edges lets the network represent several distinct flights between the same two airports with different times or costs.
在建模航线网络时,使用重边可以让网络表示同一对机场之间多条不同航班(例如时间或成本不同)。