Isopsephy

What it is

Isopsephy is a Greek practice in numerology. A word's letters carry set numbers, and those numbers are added to produce one total. That total is then set beside another name, word or verse with the same total. The match is the link between them. The term's Greek parts mean equal and count, and the old counter was a pebble. Examples survive in poetry, wall graffiti and stone inscriptions from the Greek world. It sits with other alphabetic number systems, especially Hebrew gematria and the Arabic Abjad numerals.

Where it comes from

Before Arabic numerals spread, Greek numerals were written with the alphabet. Arabic numerals came into use after Indian numerals influenced them in the eighth and ninth centuries. Fibonacci of Pisa's 1202 book Liber Abaci helped bring them to Europe. Letter-based counting had already made it easy to see numbers inside words. Apollonius of Perga, a third-century BC mathematician, posed a verse puzzle about Artemis that used multiplication. Graffiti at Pompeii from around 79 AD compare lovers by totals. A wall slogan from Rome is noted by Suetonius in 121 AD. The Book of Revelation supplies the famous 666, and its word for count shares the pebble root. Leonidas of Alexandria made paired verses with matching sums in the first century AD. A second-century gravestone from the Artemis sanctuary at Sparta Orthia gives a singing champion's verse, with each line adding to 2730. Aelius Nicon of Pergamon also composed isopsephic works.

How it is done

Greek letters are assigned units, tens and hundreds. The 24-letter alphabet was extended with three obsolete signs: digamma, also written stigma, for 6; qoppa for 90; and sampi for 900. Values are added in a line. For example, 241 can be written as sigma, mu, alpha, because 200, 40 and 1 make that sum. A word's total is then compared with another word, name or verse. Apollonius used multiplication rather than addition in his puzzle. Leonidas set a hexameter and a pentameter against the next pair so their sums agreed.

Tools and materials

The alphabet is the central instrument. It supplies 27 values from one to 900, using three obsolete letters for the gaps. Counting boards were used for arithmetic and accounts in ancient Greece, and their counter was called psephos, a pebble. Latin calculus carries the same sense, and English calculate comes from it. In the surviving examples the total is sometimes written at the end of a line, as on the Sparta stone. The number is both a result and a mark to compare.

What it is for

A shared total lets one word be read against another. The Pompeii graffiti give personal examples: one writer says his beloved's number is 545, and another gives Harmonia's name as 45. Leonidas used matching sums to address Nero in verse. The Sparta stone records a boy's singing victory and repeats the line total. Apollonius turned a verse about Artemis into a multiplication problem. The later legacy is placed in code-breaking and numerology.

Who does it

Several kinds of writer left examples. Apollonius of Perga was a mathematician. Leonidas of Alexandria was a poet who built epigrams with equal totals. Aelius Nicon of Pergamon was an architect, and his son Galen described him as skilled in geometry and numbers and as a composer of isopsephic works. Anonymous people left graffiti at Pompeii and a slogan on a Roman wall. A memorial verse for a singing champion was set up at Sparta. The practice was not confined to one profession.

Peoples and places

The Greek world is the setting for the surviving examples. They come from Alexandria, Pergamon, Sparta, Pompeii and Rome, and the verses and graffiti are in Greek. Other alphabets have related practices. Hebrew gematria applies the same broad idea to Hebrew letters. The Arabic Abjad numerals are the Arabic-alphabet counterpart. A Latin-script gematria had a following in Europe during medieval and Renaissance times. The Greek examples remain the core of isopsephy, while these relatives show the idea in other scripts.

What people believe

The practice rests on the idea that a word has a numerical side. Letters stand for fixed amounts, and a sum can be placed next to another sum. When the two agree, the words are treated as joined by that equality. Greek isos, equal, names the match. The examples in Greek verse and graffiti work through the alphabet's number scheme. The Book of Revelation uses the same counting idea in an apocalyptic Christian setting. Hebrew gematria is the closest parallel.

When it is done

The examples belong to particular moments. Pompeii graffiti link a lover to a number. A Roman wall carries a political slogan. Leonidas addresses Nero at the time of the emperor's nativity. The Sparta stone commemorates a boy's win in a singing competition. Apollonius frames his puzzle around a verse for Artemis. The examples are dated by the poems, graffiti and stones that carry them.

Compare and confuse

Isopsephy is the Greek counterpart of gematria, which works with the Hebrew alphabet. The Arabic-alphabet version is called Abjad numerals. A Latin-script gematria had a following in Europe in medieval and Renaissance times. The same broad idea appears in chronograms, where letters in an inscription stand for a date. The practice is also called isopsephism.

Today

Its stated legacy is in code-breaking and numerology. Online Greek isopsephy calculators are listed, including one that accepts Unicode Greek letters and one that totals verse lines. The old examples survive as texts and inscriptions: Pompeii graffiti, Leonidas's epigrams, the Sparta memorial and the Revelation verse. Related modern systems such as English Qaballa appear alongside it in reference lists.

Questions people ask about Isopsephy

Good reading and sources

• Isopsephy on WikipediaEncyclopedia
• Wikidata recordOpen data