Arithmancy is the study of magical properties of numbers, its a way of telling the future (like numerology) it includes number charts that are really complicated as well, its like people believe that number patterns can predict the future (PLEASE NO ONE GET FREAKED によって THIS) but its like people saying they know when the apocalypse will happen because of number patterns
Arithmancy is a Hogwarts subject taught によって Professor Vector. It comes from the Greek arithmo, meaning "number" and mancy, meaning "prophecy." This subject is taught in Classroom 7A, on the Castle's seventh floor. It is Hermione Granger's favourite subject and involves complicated number charts, but nothing else is known about the subject.
It is apparently a もっと見る accurate (or at least もっと見る accepted) way of predicting the future, similar to an obscure but existing hobby of numerology - the belief that number patterns existing in real life can be calculated to give information regarding the future. This would make it a もっと見る sensible version of Divination, at least to Hermione's taste, in that it does the same thing through もっと見る appropriate または exacting means. The accuracy of this information is unknown, however.
