Morphemeris DocsArabic Parts/Lots
What Arabic Parts (Lots) are, how they're calculated, and the seven the API offers.
Arabic Parts/Lots
Arabic Parts — also called Lots — are calculated points in the chart derived from the relationship between three factors: two planetary positions and the Ascendant. They originated in Hellenistic astrology, were transmitted and expanded by medieval Arabic astrologers, and remain an important technique in traditional astrology.
How they work
Every lot follows the same formula pattern:
Lot = Ascendant + Body A - Body BThe result is normalized to 0-360°, giving a point that falls in a specific sign and house. The lot's position in the chart is interpreted like a sensitive point — its sign, house, and aspects to planets all carry meaning.
Day/night reversal
The most important subtlety of lots is sect-based formula reversal. In a day chart (Sun above the horizon), one formula is used. In a night chart (Sun below the horizon), Body A and Body B swap:
| Day | Night | |
|---|---|---|
| Formula | Asc + Body A - Body B | Asc + Body B - Body A |
This reversal preserves the symbolic relationship between the two bodies relative to the light of the sect (the Sun by day, the Moon by night). The Morphemeris API handles this automatically based on the Sun's position relative to the horizon at the given time and location.
The seven Hermetic lots
The API offers the seven lots of Paulus Alexandrinus (Introduction, ch. 23) and Vettius Valens, the set most Hellenistic work starts from. Fortune and Spirit are built from the Sun and Moon; the other five are built from a planet and one of those two lots, so Fortune and Spirit are always computed first.
| Lot | Body A (day) | Body B (day) | Domain |
|---|---|---|---|
| Fortune | Moon | Sun | Material wellbeing, the body, circumstances |
| Spirit | Sun | Moon | Will, intellect, purpose |
| Eros | Venus | Spirit | Desire, love, what one chooses |
| Necessity | Fortune | Mercury | Constraint, obligation, enmity |
| Courage | Fortune | Mars | Boldness, force, action |
| Victory | Jupiter | Spirit | Success, trust, alliance |
| Nemesis | Fortune | Saturn | Retribution, hidden trouble, the end |
The Part of Fortune and the Part of Spirit are by far the most widely used. Fortune represents the circumstances of the body and material life; Spirit represents the soul's intent and conscious purpose. Because five lots take Fortune or Spirit as a term, asking /v1/lots for one of them brings the lot it is built on along.
Why location is required
Unlike most astronomical calculations, lots require the Ascendant — which depends on geographic location and the local horizon. This is why the /v1/lots endpoint requires lat and lon parameters.
House placement
Each lot's position falls in a house, which tells you the life domain where that lot's themes manifest. For example, the Part of Fortune in the 10th house suggests material success through career and public reputation.
API endpoint: /v1/lots (1 credit)