// Introducing graph theory in discrete Rose: In here, edges mean friendship. // Later, discussing multiple edges between the same nodes Rose: Guang, should I give the PG-13 or PG explanation? Guang: Uh... Rose: Or the R explanation? // Starts explaining Rose: *draws two nodes and an edge* So these people, at work, have a collegial relationship. *draws another edge* But behind closed doors, on the weekends, they might also have a secret sexual relationship. // Class starts laughing Rose: *drawing a loop* You can also be friends with yourself.