What is the theme in When You Reach Me by Rebecca Stead?

Friendship is another theme in the story. Miranda begins the novel by discussing her friendship with her downstairs neighbor, Sal. Miranda has been friends with Sal since she was an infant and her mother and she first moved into the apartment they still live in. However, at some point earlier in the school year, Sal decided he no longer wants to be friends with Miranda. This leaves Miranda confused, but it also forces her to befriend a girl her own age.