In astrology, a Decan is one of three equal ten-degree divisions within each thirty-degree zodiac sign. The twelve signs therefore contain thirty-six decans in total. Different astrological traditions assign planetary or sign-based rulers to these subdivisions, and the resulting associations may be used to add further symbolic detail to a planet, angle, or other chart factor located within a particular decan. Decans are a supplementary interpretive system and do not replace the primary meaning of the zodiac sign itself.