- Hermione: "Has either of you seen my copy of Numerology and Grammatica?"
- Ron: "Oh, yeah, I borrowed it for a bit of bedtime reading."
- — Ron Weasley's sarcastic response to Hermione Granger's search for her textbook[src]
Numerology and Grammatica is an Arithmancy textbook used by third-year students at Hogwarts School of Witchcraft and Wizardry. Hermione Granger briefly misplaced her copy in 1994.
In 1997, Hermione considered this book as she was sorting supplies for their mission to find Voldemort's Horcruxes. Apparently, it was one of the books she decided not to take.