Arabic Parts in Astrology: A Guide to the Hermetic Lots
Arabic Parts, more accurately called Lots, are sensitive points in a birth chart that you calculate rather than observe in the sky. They don't sit on a planet or an angle. Instead, each Lot is derived from the distance between two chart factors projected from the Ascendant, which produces a brand new point loaded with specific meaning. The most famous one is the Part of Fortune, but the tradition contains dozens, and the seven Hermetic Lots form the backbone of the system.
The name "Arabic Parts" is a bit of a historical accident. The technique is far older than the medieval Arabic astrologers who preserved it, reaching back through Hellenistic astrology to its Egyptian and Babylonian roots. Modern traditional astrologers usually call them Lots, which is the older and more accurate term. Whatever you call them, they do one thing exceptionally well: they take the raw material of a chart and concentrate a single theme, like luck, love, courage, or downfall, into one precise degree you can track, interpret, and watch by transit. This guide walks through what the Lots are, how the formula works, the seven core Hermetic Lots, and how to actually read one in your own chart.
What You'll Learn
What Arabic Parts (Lots) Actually Are
A Lot is a mathematical point, not a physical body. Where a planet is something you could point to in the night sky, a Lot is a degree of the zodiac that you arrive at by measuring the arc between two chart factors and then casting that same arc out from the Ascendant. The result lands somewhere in your chart, falls into a sign and a house, and from that moment it behaves like any other sensitive point. Planets can conjoin it, transits can hit it, and its house placement tells you where its theme plays out in your life.
The logic behind Lots is relational. A planet on its own describes one principle, but the relationship between two planets describes something more specific. The Part of Fortune, for example, captures the relationship between the Sun, the Moon, and the Ascendant all at once, then deposits that combined signal into a single point. That's why the Lots feel so targeted. Each one isolates a precise life theme that no single planet quite covers on its own.
This is also why traditional astrologers treated the Lots as essential rather than decorative. In Hellenistic practice the Lot of Fortune anchored an entire derived house system, and the other Lots gave the astrologer fast, reliable shortcuts to topics a client cared about. They aren't a fringe add-on. They're a core part of how the oldest layers of Hellenistic astrology read a chart.
How the Lot Formula Works
Every Lot follows the same three-ingredient structure. You take a starting point, add one factor, and subtract another. In practice the formula almost always reads like this:
Ascendant + Planet A - Planet B
You're working in zodiacal longitude, meaning the position of each point measured in degrees around the full 360-degree circle starting from 0 degrees Aries. You add the longitude of the first factor to the Ascendant, subtract the longitude of the second factor, and the resulting degree is where the Lot falls. If the number goes above 360 you subtract 360, and if it goes below zero you add 360, the same way a clock wraps around.
Take the Part of Fortune in a day chart as the standard example. The formula is Ascendant + Moon - Sun. If your Ascendant is at 10 degrees Cancer, your Moon at 15 degrees Leo, and your Sun at 5 degrees Gemini, you convert each to absolute longitude, run the addition and subtraction, and land on the degree where your Part of Fortune sits. The arithmetic is tedious by hand, which is exactly why a natal chart calculator is the practical way to find your Lots. The point worth understanding is the concept: the Lot preserves the exact angular relationship between the Moon and Sun, but anchors it to your specific rising degree.
That anchoring to the Ascendant matters. It's what makes a Lot personal. Two people born on the same day share a Sun-Moon relationship, but their different Ascendants throw their Parts of Fortune into completely different signs and houses, which is part of why birth time accuracy is so important for this technique.
Why Day and Night Charts Reverse the Math
Here's the detail that trips up most beginners. Many Lots have two versions of the formula, one for day charts and one for night charts, and the two factors simply swap places. The Part of Fortune is Ascendant + Moon - Sun by day, but Ascendant + Sun - Moon by night.
Whether your chart is diurnal or nocturnal depends on sect, one of the most important and most overlooked concepts in traditional astrology. If you were born while the Sun was above the horizon, in houses seven through twelve, you have a day chart. If the Sun was below the horizon, you have a night chart. This single fact changes which formula you use, and getting it wrong puts your Lot in the wrong place entirely.
The reasoning is elegant once you see it. The Lots are built on the relationship between the Sun and Moon, the two luminaries, and sect determines which luminary is the "leader" of the chart. By day the Sun leads, by night the Moon leads. Reversing the formula keeps the calculation respectful of which light was in charge when you were born. If you ever calculate a Lot and the placement feels completely wrong, the first thing to check is whether you used the correct sect-based formula.
The Part of Fortune and the Part of Spirit
Two Lots stand above the rest: the Part of Fortune and the Part of Spirit. They're a matched pair, and they reverse each other's formulas. Fortune is Ascendant + Moon - Sun by day, while Spirit is Ascendant + Sun - Moon by day, and at night the two swap. Where Fortune is the lunar Lot, Spirit is the solar one.
The Part of Fortune relates to the body, material life, fortune in the worldly sense, health, and the circumstances that happen to you. It's lunar, so it carries the Moon's flavor of fluctuation, sustenance, and the physical conditions of living. Its house placement is often read as an area where good things tend to flow toward you, and ancient astrologers used it as a launching point for an entire derived house system that examined wealth and livelihood.
The Part of Spirit, by contrast, relates to the mind, the will, career in the sense of deliberate action, and the things you actively choose to do. It's solar, so it carries the Sun's themes of vitality, purpose, and conscious direction. If Fortune is what happens to you, Spirit is what you do about it. Read together, the two Lots sketch the balance in your life between circumstance and agency, between the hand you're dealt and the way you choose to play it.
The Seven Hermetic Lots Explained
Beyond Fortune and Spirit, the Hellenistic tradition preserved a set known as the seven Hermetic Lots, attributed to Hermes Trismegistus. Each is associated with one of the seven traditional planets, and several are calculated from Fortune or Spirit rather than directly from a planet, which layers them on top of the luminary structure.
Lot of Fortune (Moon). The body, material conditions, and the fortune that arrives through circumstance. The foundation of the whole system.
Lot of Spirit (Sun). The mind, will, action, and the things you consciously set in motion. The solar counterweight to Fortune.
Lot of Eros (Venus). Desire, love, and what you long for. Calculated from the relationship between Venus and the Lot of Spirit, Eros describes the objects of your deepest wanting, in romance and beyond. It pairs naturally with the relational themes in a synastry reading.
Lot of Necessity (Mercury). Constraint, fate, and the situations you can't easily escape. Built from Mercury and the Lot of Fortune, Necessity points to the pressures and obligations that bind you, the opposite pole to the freedom Eros chases.
Lot of Courage (Mars). Boldness, daring, and the capacity to act under threat. Derived from Mars and the Lot of Fortune, Courage shows where you find your nerve and how you meet danger or competition.
Lot of Victory (Jupiter). Success, faith, and the things that expand and triumph. Built from Jupiter and the Lot of Spirit, Victory marks where optimism and winning tend to gather, and where you're inclined to push forward with confidence.
Lot of Nemesis (Saturn). Downfall, hidden weakness, and the karmic debt that catches up with you. Derived from Saturn and the Lot of Fortune, Nemesis points to limitation, loss, and the consequences that arrive on a delay. It carries some of the same weight as the karmic indicators other systems track.
Together these seven map a full emotional and circumstantial spectrum, from desire and courage at one end to constraint and downfall at the other, all anchored to the luminaries through Fortune and Spirit.
How to Read a Lot in Your Chart
Once you've calculated a Lot, you interpret it the same way you'd interpret any point in the chart, working through three layers.
First, the sign. The zodiac sign the Lot falls in colors its expression. A Lot of Eros in Scorpio wants intensely and privately, while the same Lot in Sagittarius wants adventure and freedom. The sign tells you the style.
Second, the house. This is usually the most useful layer, because the house tells you the area of life where the Lot's theme plays out. A Lot of Victory in the tenth house points success toward career and public standing. The same Lot in the seventh would route it through partnership instead.
Third, the ruler and any contacts. Look at the planet that rules the sign your Lot is in, since the condition of that ruling planet tells you how well the Lot's promise can deliver. Then check whether any planets sit on the Lot or aspect it closely. A planet conjunct your Part of Fortune is going to flavor your material life directly, for better or worse depending on the planet.
Finally, the Lots come alive in prediction. When a transit or a profected year activates the degree of a Lot, the theme of that Lot tends to surface in real events. A transit to the Lot of Eros can coincide with a new attraction. A hard transit to the Lot of Nemesis can mark a reckoning. This is where the Lots stop being a curiosity and start earning their place in a working practice.
Arabic Parts in Traditional vs Modern Astrology
Modern Western astrology largely set the Lots aside during the twentieth century, keeping only the Part of Fortune and often treating even that as a minor point. The psychological turn in astrology favored planets and aspects as symbols of inner experience, and the calculated, event-oriented Lots didn't fit that frame as neatly.
The traditional revival of the last few decades brought them roaring back. Astrologers working in the Hellenistic style treat the Lots as indispensable, especially for timing techniques like annual profections and zodiacal releasing, where the Lots of Fortune and Spirit serve as starting points for reading the chapters of a life. If you've only ever encountered astrology through the modern lens, the Lots can feel like a hidden layer of the chart you never knew was there, and many people find they add a precision that planet-only readings lack.
You don't have to choose one school over the other. Plenty of astrologers blend a modern psychological reading of the planets with a traditional reading of the Lots, using each for what it does best. The planets describe who you are. The Lots describe specific themes and where they land. Used together, they make the chart sharper than either approach manages alone.
Frequently Asked Questions
What is the difference between Arabic Parts and Lots?
There's no difference in the technique, only in the name. "Lots" is the older and more accurate term, going back to Hellenistic astrology. "Arabic Parts" is the name that stuck in the English-speaking world because medieval Arabic astrologers preserved and expanded the system, but they didn't invent it. Most traditional astrologers today prefer "Lots."
How many Arabic Parts are there?
There's no fixed number. The seven Hermetic Lots form the core, but medieval astrologers calculated hundreds of additional Lots for highly specific topics, from marriage and children to illness, travel, and even the price of grain. Most practicing astrologers focus on Fortune, Spirit, and a handful of the others rather than the full catalogue.
Do I use the day or night formula for my Lots?
Use the day formula if you were born while the Sun was above the horizon, and the night formula if it was below. This is determined by sect. A quick check is the Sun's house: roughly speaking, a Sun in houses seven through twelve is a day birth, and a Sun in houses one through six is a night birth. Getting this right is essential, since the wrong formula puts the Lot in the wrong place.
Is the Part of Fortune the most important Arabic Part?
Yes, in most traditional systems the Part of Fortune is the most important Lot. It relates to the body and material life, and it anchored an entire derived house system in Hellenistic practice. The Part of Spirit is its essential counterpart. If you only ever work with two Lots, those are the two to learn first.
Can I calculate Arabic Parts without knowing my birth time?
Not accurately. Every Lot is cast from the Ascendant, which moves about one degree every four minutes and depends entirely on your exact birth time. Without an accurate time the Ascendant is uncertain, and the Lots calculated from it become unreliable. If you're unsure of your birth time, the Lots are one of the techniques most affected by that gap.
The Lots are one of the oldest and most practical tools in the astrological toolkit, and they reward the small effort it takes to learn them. Start with Fortune and Spirit, get comfortable reading them by sign and house, then add the Hermetic Lots one at a time as the themes become familiar. Generate your natal chart to find where your Lots fall, pull a tarot reading when a transit activates one and you want a second angle on what's surfacing, and run the compatibility tool to see how the relational Lots like Eros play out between two charts. The planets tell you who you are. The Lots tell you where the story lands.