Arithmancy is a rather unusual term used to describe a type of divination that involves the use of numbers. While there are not many direct synonyms for this word, there are several related terms that could be used in its place. For example, numerology is a similar practice that also involves interpreting numerical patterns and sequences to gain insight into the future. Another related term could be divination, which is the broader category of practices that includes Arithmancy and other forms of fortune-telling. Finally, mathematics could be considered a synonym for Arithmancy, as it involves the study and manipulation of numbers in a variety of ways.