Merriam-Webster's Online Dictionary defines "synecdoche" as: "a figure of speech by which a part is put for the whole (as fifty sail for fifty ships), the whole for a part (as society for high society), the species for the genus (as cutthroat for assassin), the genus for the species (as a creature for a man), or the name of the material for the thing made (as boards for stage)."
The title to this movie is a play on Schenectady, New York, where the movie takes place. Schenectady, New York has the distinction of having the ZIP code 12345.
Synecdoche is pronounced: si-nek-duh-kee (with a stress on "nek").
Philip Seymour Hoffman's character's last name is a reference to the Cotard delusion or Cotard's syndrome, also known as nihilistic or negation delusion, which is a rare neuropsychiatric disorder in which a person holds a delusional belief that he or she is dead, does not exist, is putrefying or has lost his/her blood or internal organs.
When Caden sees Hazel at the box-office, a brief shot reveals she is reading: page 1 of Marcel Proust's Swann's Way, the first book of his multi-volume novel Search of Lost Time. A recurring character throughout Proust's novel is Dr. Cottard, reportedly based somewhat on Proust's own father, a noted physician, and on the Cotard who gives the delusional syndrome it's name.
At the start of the film, when 'Phillip Seymour Hoffman' is reading the news at the breakfast table, he reads out that "Harold Pinter has died.... wait.... no - he's won the Nobel prize". This is a reference to a famous Sky News clip whereby Sky, in their rush to be first with breaking news, accidentally announced that Harold Pinter was dead. In fact it had just been announced that he was to be awarded the Nobel prize for literature.
The film was originally set to be directed by Spike Jonze, who chose to direct _Where the Wild Things Are (2009)_ instead.
Charlie Kaufman's directorial debut.
Dianne Wiest appears after an hour and twenty minutes into the film. Even then, she only gets ten minutes of screen time, despite prominent billing.