Decanate

Each of the twelve signs consists of 30 degrees. Decanates (or decans) are the division of these 30 degrees into three groups of 10 degrees, amounting to 36 decanates in all. When using the Equal House system of division the houses of the birthchart can also be divided into 36 decanates.

The first 10 degrees of any sign or house (0-9) are always called the first decanate, likewise the second ten degrees (10-19) the second decanate and the last ten degrees (20-29) the third decanate.

Each decan of a sign expresses subtle differences that distinguish it from the other two decans as described by its planetary sub-ruler, which operates in conjunction with the natural planetary ruler of the sign. The first decan of a sign is sub-ruled by the natural ruler of the sign; the second decan is sub-ruled by the ruler of the next sign in the zodiac that belongs to the same triplicity; the third decan is sub-ruled by the ruler of the remaining sign in that triplicity.