So, Cistercian Numerals: Decoding an Antique Number System

This week, decode an ancient and uncommon European numeral system that uses overlapping glyphs



Cisterian numerals—sometimes referred to as a Cistercian cipher or Monk cipher—is an obscure medieval numeral system that is similar to traditional Hindu-Arabic numerals. Unlike the rapid widespread acceptance of Arabic numerals, Cistercian numerals were only found in a few regions of Europe during a short period of time, even during its height in limited popularity. The numerals were likely developed in response to the introduction of the foreign Hindu-Arabic math symbols into Europe by a rival religion during the early 13th century and originated in Cistercian monasteries in Hainault, London. Traditionally, the Cistercian numerals were used for numbering pages in the corners of manuscripts or displaying years rather than arithmetic, where Arabic numerals were vastly more versatile. In Arabic numerals, the value one is represented as 1, two is 2, and so on, and can represent any rational number. Unlike Arabic numerals, a single glyph in Cisterican numerals can only represent values from 1 to 9999. The system was rarely used outside of the Cistercian order and was largely abandoned by the 16th century.

Each number in the Cisterian system is broken up into a value between 1-9 and is indicated by a unique glyph built from the central stave. The units of the number (units, tens, hundreds, or thousands) are indicated by the position relative to the stave. The same shape is used facing a new direction to indicate its new digit. So, the value 5*, 50, 500, and 5000 are the same shape in four different positions. A more complex number is created by breaking apart the value into its units, tens, hundreds, and thousands and then combining them into one glyph. While zero is not defined as a value in the Cisterian cipher, the absence of a symbol is read as zero. 

Historically, most Cisterian glyphs used a horizontal stave and were read from right to left and top to bottom as units (U), tens (T), hundreds (H), thousands (K).

A vertical stave was prevalent during its brief revival in the 18th-20th century as well as in Northern France during the 14th and 15th century. For vertical staves, the values are 90° counterclockwise from how they are presented in the horizontal form and are typically read top to bottom and left to right left as units (U), tens (T), hundreds (H), thousands (K)

So, with a horizontal stave, the value 1969 is written by combining the units (9), tens (60), hundreds (900), and thousands (1000) together into a single glyph.



*In some surviving manuscripts, 5 is written as a dot (꜎) instead of a staff