Dodekatemoirion (sing.) or dodekatemoiria (pl) (or dodecatemoirion, etc.)
The literal meaning of the Greek word is 'twelfth part', for which reason the word is sometimes used in Greek texts to describe the 12 signs of the zodiac, each being a twelfth part of the zodiacal ring. However, it also describes a specific, mystical technique (which has a strong presence in ancient Babylonian and cuneiform texts), which sees each sign as being capable of acting as a micro-zodiac, by the division of each sign into twelve equal parts of 2˝° degrees. The multiplication of these points by 12 is then expected to identify associated points between this symbolic micro-zodiac and the actual zodiac. For example, imagine a planet at 10° Taurus - the number of degrees (10) is multiplied by 12 to obtain 120° - its dodekatamorion will lie 120° ahead of it in the zodiac.
Two variants of the method are described by Paulus (Introductory Matters, 22) and Firmicus (Mathesis, I.XIII). The latter, projects the result of the calculation from the beginning of the sign in which the planet is positioned, so (starting the count of 120° from 0° Taurus) the dodekatemorion of 10° Taurus would be 10° Virgo. The former method of Paulus projects the result of the calculation from the position of the planet, so (starting the count of 120° from 10° Taurus) the dodekatemorion of 10° Taurus would be 20° Virgo - another way to describe this (which is how Paulus describes it) is to multiply the degree position by 13 instead of 12 and then start the count from the beginning of the sign - the mulitplication by 13 accommodates the fact that the count is starting from the position of the planet rather than the beginning of the sign.
Hence commentators generally talk about the two variants being distinguished by multiplication of 12 or 13, but this misses the fundamental point: the symbolism is always determined by the act of multiplying by 12, what appears to be confused according to alternate accounts, is where the count ought to begin. In my opinion, it only makes sense to project the result of the calculation from the point being progressed, and not the beginning of the sign, so I believe that Paulus leads us to the correct result, but by making reference to multiplication by 13, he obscures the reason why this is correct - which is simply because it adds the result of the 12-fold mutlipication to the position of the planet. Paulus gives the example of 11° Aries: multiply 11° by 12 = 132°, add these degrees to 11 Aries and the result is what he describes: 23° Leo.
Paulusand Firmicus both tell us that the dodekatemorion of the benefic planets bring good fortune if they fall upon the position of the Sun, Moon Mercury, the angles, Part of Fortune, etc, and likewise the dodekatamorion of malefic planets will be expected to bring damage when they fall upon the chart's sensitive degrees.
Read Francesca Rochberg's comments on the Babylonian use of dodekatemoira (Google books).
© Deborah Houlding