Arithmancy is a magical discipline that studies the magical properties of numbers, including (but not limited to) predicting the future with numbers and numerology. Those who practiced Arithmancy were called Arithmancers.
Arithmancy was an elective subject offered from the third year on at Hogwarts School of Witchcraft and Wizardry, the homework assignments of which included writing essays that required the consultation and/or composition of complex number charts.
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