Key Terms

Ephemeris. A table that lists the daily positions of the planets. Astrologers use it to find where each planet is in the zodiac on any given day. Modern practice mostly uses software, but the printed ephemeris is still the foundation.

Tropical zodiac. The most commonly used zodiac in Western astrology. It is aligned with the seasons and the equinoxes rather than the actual constellations. The first degree of Aries is the moment of the spring equinox. The tropical system is symbolic, tied to the cycle of light rather than the literal star groupings.

Sidereal zodiac. An alternative zodiac aligned with the actual positions of the constellations. Used primarily in Vedic astrology and in some Western traditions. Due to the precession of the equinoxes, the sidereal positions are currently about 24 degrees behind the tropical positions.

Precession of the equinoxes. A slow wobble in Earth's axis that causes the equinox points to shift backward through the zodiac by about one degree every seventy-two years. This is why the tropical and sidereal zodiacs no longer match. Precession is also the basis of the astrological "ages" (Age of Pisces, Age of Aquarius).

Age of Aquarius. The current astrological age, beginning sometime in the late twentieth or early twenty-first century depending on the calculation system. Each age lasts roughly 2,160 years. The Age of Pisces preceded it. The themes of each age reflect the symbolism of the sign.

The ecliptic. The apparent path the Sun travels across the sky over the course of a year. The zodiac is divided into twelve thirty-degree sections along the ecliptic. All planets travel close to the ecliptic plane.

Zodiac. The band of sky surrounding the ecliptic, divided into twelve signs of thirty degrees each. The zodiac is the frame on which everything else is measured.

Natal chart. Also called the birth chart or radix. The map of the sky at the exact moment and place of a person's birth. The natal chart is the foundation document of any astrological work.

House systems. Different methods of dividing the sky into the twelve houses. The most common systems include:

• Placidus. The standard modern house system. Uses unequal house sizes based on time. Most popular in mainstream Western astrology.
• Whole Sign. An older system, now widely used again. The sign on the Ascendant becomes the entire first house. Each subsequent sign becomes the entire next house. Houses are exactly thirty degrees each.
• Equal House. Each house is thirty degrees, starting from the Ascendant degree.
• Koch. Similar to Placidus but with different math.
• Regiomontanus, Campanus, Porphyry. Older systems still used by some practitioners.

The choice of house system can change the house position of planets near house cusps. Each system has its strengths. Most modern Western practitioners use Placidus or Whole Sign.

Cusp. The boundary between two houses or two signs. A planet near a cusp can be read either as belonging to the house it sits in or as influencing the next house, depending on the system and the orb.

Orb. The margin of effective influence around an aspect or a cusp. Tighter orbs produce stronger effects. The convention varies, but for major aspects involving personal planets, modern practice uses orbs of 5 to 8 degrees. The Sun and Moon are given wider orbs (up to 10 degrees). Minor aspects get tighter orbs (2 to 3 degrees).

Degree. Each sign contains thirty degrees, and each degree contains sixty minutes. Planetary positions are typically written as sign, degree, minute. For example, 15 degrees 23 minutes of Aries (15°23′ Aries). For precise work, degrees can also be broken down into seconds.

Decanate. A division of each sign into three ten-degree sections. Each decanate is associated with a planetary sub-ruler that adds nuance to the sign expression. Some traditions assign the decanates to the signs of the same triplicity (element). Other systems use the Chaldean ordering of planets.

Ingress. The moment a planet enters a new sign. Ingresses are timing points that often correlate with collective events. The Sun's ingress into each sign marks the start of the corresponding zodiacal season.

The planets have a set of traditional relationships with the signs that describe how comfortably they operate in each sign. This is called dignity.

Domicile (Rulership). A planet is in domicile when it is in the sign it rules. The Sun in Leo. The Moon in Cancer. Mars in Aries or Scorpio. The planet operates at full strength and natural ease.

Exaltation. A planet is exalted when it is in a sign that amplifies its function. The Sun is exalted in Aries. The Moon in Taurus. Mercury in Virgo. Venus in Pisces. Mars in Capricorn. Jupiter in Cancer. Saturn in Libra. Exaltation produces particular brilliance in the planet's function.

Detriment. A planet is in detriment when it is in the sign opposite the sign it rules. The Sun in Aquarius. The Moon in Capricorn. Mars in Libra or Taurus. The planet operates against its grain. The expression is still real but requires more conscious work.

Fall. A planet is in fall when it is in the sign opposite its exaltation. The Sun in Libra. The Moon in Scorpio. Mercury in Pisces. Venus in Virgo. Mars in Cancer. Jupiter in Capricorn. Saturn in Aries. The planet operates at a disadvantage and tends to express through the more difficult or shadow side of its function.

Peregrine. A planet with no dignity or debility in its current sign. Operates without enhancement or impediment.

Mutual reception. When two planets are each in the sign the other rules. Mercury in Pisces and Neptune in Gemini, for example, would be in mutual reception. The two planets effectively exchange places of strength and support each other.

Traditional rulership. The classical assignment of planets to signs: Mars rules Aries and Scorpio, Venus rules Taurus and Libra, Mercury rules Gemini and Virgo, the Moon rules Cancer, the Sun rules Leo, Jupiter rules Sagittarius and Pisces, Saturn rules Capricorn and Aquarius. The system in use before the discovery of Uranus, Neptune, and Pluto. Each of the seven classical bodies has either one (the lights) or two (the other five) signs.

Modern rulership. The modern reassignment of the three night-side signs to the outer planets: Uranus rules Aquarius, Neptune rules Pisces, Pluto rules Scorpio. Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Sagittarius and Capricorn keep their classical rulers. Modern practice usually treats the outer rulerships as primary in those three signs while still acknowledging the classical ruler as co-ruler.

Hybrid rulership. A practice that uses the modern ruler as primary for Aquarius / Pisces / Scorpio but retains the classical ruler as a half-weight co-ruler. So under hybrid mode a Scorpio Ascendant has Pluto as its primary chart ruler and Mars as a secondary, both contributing to chart dignity. The Asteria signature reading runs in this hybrid mode under the modern toggle.

Asteroid co-rulership. A modern proposal that the named asteroids each carry a sign affinity. Ceres co-rules Taurus and Virgo. Pallas, Libra and Aquarius. Juno, Libra and Scorpio. Vesta, Virgo and Scorpio. Chiron is sometimes given Sagittarius and Virgo. These co-rulerships are additive, not replacement: Pluto is still the primary ruler of Scorpio under modern, with Juno and Vesta adding texture. There is no firm consensus across schools; different practitioners assign different signs.

Direct motion. A planet moving forward through the zodiac at its standard pace. The default state.

Retrograde motion. A planet appearing to move backward through the zodiac due to the relative motion of Earth and the planet. See the retrograde file for full treatment.

Stationary. A planet appearing to stop in the sky just before or after changing direction. Extremely powerful in influence.

Combust. A planet within roughly 8 degrees of the Sun. The planet is overwhelmed by the solar light and tends to lose visible function. Mercury and Venus are most often combust because they orbit close to the Sun.

Cazimi. A planet within 17 minutes (less than one degree) of exact conjunction with the Sun. Traditional astrology considered this a position of unusual blessing, the opposite of combust. The planet is "in the heart of the Sun" and gains exceptional power.

Under the beams. A planet within roughly 15 degrees of the Sun. Visibility is impaired but less drastically than combust.

Out of bounds. A planet whose declination exceeds the Sun's maximum declination (about 23 degrees 27 minutes). Most planets stay within this range. When a planet goes out of bounds, it operates with unusual freedom and intensity, often producing exceptional or extreme expressions of its function. The Moon is most commonly out of bounds.

Void of course Moon. A period when the Moon has made its last aspect before leaving a sign and is moving toward the next sign without making any more major aspects. Traditional practice considers this a quiet, unproductive period for starting new things. Best used for rest, routine, or reflection.

Antiscia. A symmetry point. Each degree of the zodiac has an antiscia partner across the solstice axis (Cancer/Capricorn 0°). Planets in antiscia relationship to each other have a subtle connection that some astrologers read as similar to a conjunction.

Transit. The current movement of a planet in the sky, often read in relationship to the natal chart. When transiting Saturn moves through the natal seventh house, for example, the themes of Saturn (structure, commitment, restriction) are active in the area of partnership for that period.

Progression. A predictive technique that advances the natal chart according to a formula. The most common is secondary progressions, where each day after birth represents a year of life. The progressed chart describes the slow internal unfolding of the natal chart over the lifetime.

Solar arc. Another progression technique where every planet moves forward at the rate of the secondary progressed Sun (about one degree per year). Solar arc directions are often used for predictive timing of major events.

Solar return. A chart drawn for the moment the Sun returns to its exact natal position each year (around the birthday). The solar return chart is read as a forecast for the year ahead.

Lunar return. A chart drawn for the moment the Moon returns to its exact natal position each month. Used for monthly forecasting, especially around emotional themes.

Eclipse. A new moon (solar eclipse) or full moon (lunar eclipse) that occurs when the Sun, Moon, and lunar nodes are in close alignment. Eclipses produce stronger effects than ordinary lunations and tend to mark significant turning points. Eclipses repeat in cycles called Saros series.

Lunation. The monthly cycle of the Moon, including the new moon, the first quarter, the full moon, and the last quarter. Each lunation activates the houses where the new and full moons fall in the chart.

Aspect by transit. When a transiting planet forms a major aspect to a natal planet. These are the timing markers of life. A transiting Saturn square to the natal Sun, for example, often marks a period of significant pressure on the central identity.

Synastry. The comparison of two natal charts, looking at the aspects between the two sets of planets. Used primarily for relationship analysis. Tells you how two people's planetary functions interact.

Composite chart. A third chart created by taking the midpoint between each pair of planets in two natal charts. The composite chart represents the relationship itself as a third entity, with its own dynamics and trajectory.

Davison chart. Another method of creating a relationship chart, using the actual midpoint in time and space between the two birth moments. Some astrologers prefer Davison over Composite.

Relocational astrology. A technique that redraws the natal chart for a different location. The signs and planets stay the same, but the angles change, which changes the house positions. Used to assess how a person experiences different geographic locations.

Astrocartography. A specific form of relocational astrology that maps planetary lines across the globe. Each planet has lines where it is on the angles (Ascendant, Midheaven, Descendant, IC) at various locations. Living on or near a planetary line tends to activate that planet's function in the life. The classical set is the ten planets across four angles: forty lines. Modern practice often adds Chiron, the lunar Nodes, and Black Moon Lilith to the line set, giving fifty-two lines in total.

Parans (paran latitudes). A paran, from the Greek for "side by side", is the latitude at which two of your astrocartography lines cross. Anywhere along that latitude band carries the hybrid signature of those two planets, regardless of which longitude you pick. So a Venus-on-the-Ascendant × Jupiter-on-the-Midheaven paran at 34° North means Venus rising while Jupiter culminates anywhere along that 34° N band, Los Angeles, Cairo, Shanghai, every spot on the line gets a flavour of that combined energy. Parans are part of the original Jim Lewis AstroCartoGraphy system and are the strongest answer to "what if I'm not on a line but my chart still feels activated here."

Mundane astrology. The branch of astrology that deals with collective events: nations, leaders, economies, weather, history. Mundane charts include the charts of countries (based on independence or constitution dates), ingress charts for major events, and the long-cycle planetary returns.

Stellium. Three or more planets in a single sign or single house. Creates a concentrated theme in that area of the chart.

Stellium dispositor. The ruler of the sign that holds the stellium. If three planets sit in Taurus, Venus disposes them: Venus's condition (sign, house, aspects) ends up steering the whole stellium, because the three planets at one level "report to" Venus at the next. Dispositorship turns the chart into a small hierarchy. Tracing the dispositor chain, Venus in Cancer is disposed by the Moon, the Moon's sign is disposed by its ruler, and so on, sometimes lands on a single planet that ultimately steers the whole chart.

Singleton. A single planet alone in an element, mode, or hemisphere. Often produces an extreme expression of that function.

Anaretic degree. The 29th degree of any sign, considered a critical or transitional point. Planets at the anaretic degree often produce themes of urgency, completion, or unfinished business.

Critical degrees. Specific degrees considered traditionally significant. The cardinal degrees (0° of Aries, Cancer, Libra, Capricorn) are the strongest. The 13° and 26° of fixed signs and the 4° and 17° of mutable signs are also considered critical.

Aspect pattern. Three or more planets connected by aspects forming a recognizable geometric shape (T-square, Grand Trine, Kite, Yod, etc.). See the aspects file for full treatment.

Karmic axis. The line between the South Node and North Node, marking the soul's evolutionary direction. See the planets file for full treatment.

Saturn return. The period when transiting Saturn returns to its natal position, occurring around ages 28-30, 58-60, and 87-90. The first Saturn return is one of the most significant transits in adult life.

Chiron return. The period when transiting Chiron returns to its natal position, occurring around age 50. The convergence with the original wound from the perspective of half a life lived.

Uranus opposition. The period around age 40-42 when transiting Uranus opposes its natal position. The astrological signature of the classic midlife crisis.

Personal planets. Sun, Moon, Mercury, Venus, Mars. The fast-moving planets that describe the personality.

Social planets. Jupiter and Saturn. The mid-paced planets that describe how the person engages with society.

Outer planets. Uranus, Neptune, Pluto. The slow-moving planets that describe generational and collective themes, plus their personal effects through aspects and house positions.

Luminaries. The Sun and the Moon. The two brightest objects in the sky and the two most important points in any chart.

Malefic. Traditional name for the difficult planets: Mars and Saturn (lesser and greater malefic). Modern astrology no longer treats them as simply bad, but the term persists.

Benefic. Traditional name for the helpful planets: Venus and Jupiter (lesser and greater benefic).

Angular houses. The 1st, 4th, 7th, and 10th houses. The most active and visible houses in the chart.

Succedent houses. The 2nd, 5th, 8th, and 11th houses. The houses that follow the angular houses and consolidate their themes.

Cadent houses. The 3rd, 6th, 9th, and 12th houses. The houses of transition and dissolution, leading into the next angular house.

The Ascendant ruler. The planet that rules the sign on the Ascendant. This planet is the chart ruler. Its position by sign, house, and aspect is one of the most important features of the entire chart.

The 12 letter alphabet. A teaching framework that maps each sign to a planet (its ruler) and a house (the natural house of that sign). Aries-Mars-1st house. Taurus-Venus-2nd house. Gemini-Mercury-3rd house. And so on. This framework is used to draw parallels between sign expression, planetary function, and house arena.

A chart's dominant planet, dominant sign, and signature sign are answers to a single question: of all the bodies and signs in this chart, which ones actually steer the person? The Sun and the Moon always carry weight, but in a particular chart it may really be Pluto on the Ascendant, Saturn ruling three planets, or a Venus in the 10th that does the actual driving. The signature reading is the whole-chart shape, distinct from the Sun, the Moon, or the Rising.

Dominant planet. The planet that carries the most weighted score in the chart. The weighting blends sign placement (with dignity), house placement (angular > succedent > cadent), aspects (with closer orbs counting more), rulership of the chart's key points (ASC, MC, Sun-sign, Moon-sign), sect status, and condition modifiers. The strongest body sits at the top of the dominance ranking. Most charts have the Sun or Moon in the top three; only an unusually dignified angular planet can displace a light.

Dominant sign. The sign that carries the most weighted planetary placement. Computed by summing the per-body weights of every planet that lands in each sign, plus the Ascendant and Midheaven votes. A chart with three planets in Scorpio and the Ascendant in Scorpio has Scorpio as a strong dominant sign even when the Sun is elsewhere.

Signature sign. The single sign that summarises the whole chart's gestalt. Derived by finding the chart's dominant element (Fire / Earth / Air / Water) and dominant modality (Cardinal / Fixed / Mutable) and looking up the sign at their intersection. Fire + Cardinal = Aries. Earth + Fixed = Taurus. Water + Mutable = Pisces. Often the signature matches the Sun, the Moon, or the Rising: when it does the chart agrees with its own surface. When it doesn't, the signature is the quieter shape underneath those three, and the mismatch is usually the most useful sentence in the reading.

Pullen scoring. The method of dominance scoring popularised by Walter Pullen's Astrolog program (and surfaced on astro.com under "Simple chart delineation"). Each planet gets a Position subtotal (sign + house + dignity + rulership + condition) and an Aspects subtotal (orb-weighted contact count), summed into a Total. The Total is then expressed as a Percent, the planet's share of the total chart steer, with all bodies summing to 100%. Pullen's exact numeric constants are unpublished, but the structure, Position + Aspects + Total + Percent, is the standard breakdown.

Position score. The half of a Pullen-style total that comes from sign, house, dignity, rulership, sect, and condition. Everything except aspect participation. This is the "where does this planet sit and what does it rule" component of dominance.

Aspect score. The half of a Pullen-style total that comes from the orb-weighted count of major aspects this planet makes. Tighter aspects count more; the total per planet is capped so a single busy body cannot run away with the score on aspects alone.

Element balance. The weighted distribution of a chart's bodies across Fire, Earth, Air, and Water. Computed by summing each body's element-weight vote (Sun, Moon, Ascendant heaviest; outers lightest) into its sign's element. The dominant element feeds the signature sign.

Modality balance. The weighted distribution of a chart's bodies across Cardinal, Fixed, and Mutable. Same weighting as element balance; the dominant modality is the other half of the signature sign formula.

Element blend / modality blend. When the runner-up element or modality sits within ~8 percentage points of the leader, the chart carries the blend in practice. A Fire-Water blend is the chart of someone who initiates from feeling. A Fixed-Cardinal blend is the chart of someone who starts things and then refuses to let them shift.

This is the working vocabulary. Memorize what is useful. Cross-reference as needed. The language is a tool. The chart is the territory. The work is to use the tool to read the territory more clearly.

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The technical vocabulary is the toolkit. The reading is the craft. The terms make the reading possible. The reading makes the terms come alive.