In astrology, each zodiac sign (30°) is divided into three equal parts of 10° each, called decans. Each decan has its own sub-ruler planet, adding nuance and specificity to the interpretation of a planet’s placement in a sign.
Understanding decans allows astrologers to provide more detailed personality traits, tendencies, and life influences.
1. Structure of Decans
Decan | Degree Range | Sub-Ruler / Influence | Key Traits |
|---|---|---|---|
| 1st Decan | 0° – 10° | Sign’s primary ruler | Pure expression of the sign’s core traits |
| 2nd Decan | 10° – 20° | Sign’s next same-element ruler | Adds secondary qualities of similar element signs |
| 3rd Decan | 20° – 30° | Third same-element ruler | Adds tertiary qualities, additional nuance |
2. Example: Aries Decans
Decan | Degree | Ruler | Traits |
|---|---|---|---|
| 1st | 0°–10° | Mars | Bold, energetic, impulsive, initiator |
| 2nd | 10°–20° | Sun | Leadership, creativity, ambition |
| 3rd | 20°–30° | Jupiter | Optimism, adventurous, expansive energy |
3. How to Use Decans in Chart Interpretation
- Determine the degree of the planet within the sign.
- Identify the decan it occupies → this reveals subtle traits and influences.
- Combine with main sign ruler, modality, element, and house placement → for a richer, more precise interpretation.
- Especially useful for personal traits, temperament, and psychological nuances.
✅ Summary
Decans divide each sign into three 10° segments, each with a sub-ruler. They add detail and nuance to the interpretation of planetary placements, refining the understanding of personality, tendencies, and life themes.
