Maybe you’ve used the phrase yourself: "It’s purely platonic." Plato would not be impressed. The word he lent his name to was supposed to mean a love so powerful it transcends the physical. Marisa G. Franco is a psychologist, and a professor at the University of Maryland. She is the author of the book Platonic: How the Science of Attachment Can Help You Make – and Keep – Friends.

Something is happening to men that’s leading them to have fewer friends than women. Producer Arman Aghbali looked into two recent books examining friendship among men: Hua Hsu is the author of Stay True. Michael Pedersen is the author of Boy Friends.