The original title of Ovid's book was "Metamorphoseon Libri XV," or "Fifteen Books of Metamorphoses." You know how some people think things sound smarter or classier if they're said in French? Well, back in Ovid's day, some Romans tried to get the same effect by speaking Greek. Apparently, Ovid was one of those Romans. Actually, though, he didn't take his geeky Greekiness all the way: "Libri XV," which means "Fifteen Books," referring to the poem's division into fifteen chapters (a.k.a. "books"), is as Latin as it comes. As for the "Metamorphoseon" part, we just hope its added bit of Greek pizzazz convinced some ancient Roman to shell out a few extra coins at the book-vendor. Really, we don't think he'd be disappointed.
"Metamorphosis" means "changing-of-shape" (think about a caterpillar, which undergoes metamorphosis to become a butterfly), so Ovid's book is really just about things changing into other shapes. The fact that he makes the title half-Latin and half-Greek might just be a sneaky way of owning up to the fact that most of the stories in the book are of Greek origin, though towards the end you get more and more Latin ones as well. All the same, though, we at Shmoop think "Metamorphoseon Libri XV" is a bit of a mouthful, so we're happy that, over time, the book has acquired its own standard title in English: "The Metamorphoses."