In 325 AD, following the First Council of Nicaea, departures from the beliefs of the state church were classified as civil violations within the Roman Empire. It was officially adopted in Egypt during the reign of Ptolemy II Philadelphus (284–246 BCE). The Milesian system was in common use by the reign of Alexander the Great (336–323 BCE) and was adopted by other cultures during the subsequent Hellenistic period. Pythagoras was a contemporary of the philosophers Anaximander, Anaximenes, and the historian Hecataeus, all of whom lived in Miletus, across the sea from Samos. Aristotle wrote that the Pythgoraean tradition, founded in the 6th century by Pythagoras of Samos, practiced isopsephy, the Greek predecessor of Hebrew gematria. Early examples include vase graffiti dating to the 6th century BCE. The practice of using alphabetic letters to represent numbers developed in the Greek city of Miletus, and is thus known as the Milesian system.

An Assyrian inscription from the 8th century BC, commissioned by Sargon II declares 'the king built the wall of Khorsabad 16,283 cubits long to correspond with the numerical value of his name.' Rabbinic literature used gematria to interpret passages in the Hebrew Bible. The practice of gematria, assigning numerical values to words and names and imputing those values with religious meaning, dates back to antiquity. Although the word 'arithmancy' dates to the 1570s, the word 'numerology' is not recorded in English before c. 'Αριθμομαντεία' Arithmancy is thus the study of divination through numbers. The term arithmancy is derived from two Greek words – arithmos (meaning number) and manteia (meaning divination). For example, in his 1997 book Numerology: Or What Pythagoras Wrought ( Dudley 1997), mathematician Underwood Dudley uses the term to discuss practitioners of the Elliott wave principle of stock market analysis. The term numerologist can be used for those who place faith in numerical patterns and draw inferences from them, even if those people do not practice traditional numerology. It is often associated with the paranormal, alongside astrology, and is similar to divinatory arts.

When numerology is applied to a person's name, it is a form of onomancy. It is also the study of the numerical value, via an alphanumeric system, of the letters in words and names. Numerology (known prior to the 20th century as arithmancy) is the belief in an occult, divine or mystical relationship between a number and one or more coinciding events. Numerorum mysteria (1591), a treatise on numerology by Pietro Bongo and his most influential work in Europe For the wireless communication term, see Numerology (wireless). For the concept in Ismailism, see Numerology (Ismailism).

Bible numerology chart