These divisions are known as the "decans" or "decanates" and cover modifications of individual traits, attributed to minor planetary influences, which temper or blend with the ruling influence of the period.
[1][better source needed] Each sign is allocated a triplicity, consisting of three of the four classical elements air, water, earth or fire, and is therefore subdivided into three equal parts of 10 degrees each; these parts are referred to as decans or decanates.
Notice that rulerships follow a repeating pattern, the Chaldaean order of the planets: Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon, based on a geocentric cosmological model.
Decans or "faces" are the least important of the essential dignities, representing about one-fifteenth of a planet's overall strength in medieval astrology.
[4][better source needed] The decans and their rulers are assigned as follows as based on the concepts of modern Western astrology :