Astrology glossary: every term explained

By Nadia Reyes

Astrological vocabulary names one of three things: a position (where a planet was), a technique (how the position is calculated or compared), or an interpretation (what a tradition says the position means). Positions and techniques have fixed, checkable definitions. Interpretations vary by school and by century. The terms used most often across this section are defined below, alphabetically. Where a term has its own page, the entry links to it.

What do astrology terms mean?

The vocabulary comes in layers, and knowing which layer a word belongs to explains most of the confusion around it.

The oldest layer is Hellenistic Greek, roughly the second century BC to the fifth century AD — sect, domicile, exaltation, the lots, the twelve houses. Vettius Valens, writing around 150 AD, and Claudius Ptolemy in the second century are the two surviving sources most modern practice descends from. A second layer arrived through Arabic-language astrologers, Abu Ma'shar in the ninth century chief among them, who preserved and extended the Greek material. A third is early modern English: William Lilly's Christian Astrology of 1647 is where most of the horary vocabulary in current use comes from. The newest layer is twentieth century and psychological — terms like "chart ruler as personality theme", the reading of the Moon as emotional life, and most of what Sun-sign columns are built on.

Words from the astronomical layer mean exactly one thing. Words from the interpretive layers mean what a given tradition says they mean, and traditions disagree.

What does each astrology term mean, A to Z?

A

Air signs — Gemini, Libra and Aquarius, the three signs grouped under the element of air.

Angles — the four most structurally important points in a chart: the Ascendant, Descendant, Midheaven and Imum Coeli. They depend on the exact minute and place of birth.

Applying — an aspect still forming, the faster planet moving toward exact. Traditional astrology treats applying aspects as active and separating ones as spent.

Ascendant — the degree of the zodiac rising over the eastern horizon at the moment and place of birth. Also called the rising sign. It moves about one degree every four minutes, which is why birth time matters.

Aspect — an angular relationship between two planets measured along the zodiac, such as 90 or 120 degrees. Ptolemy set out the five classical aspects; later astrologers added smaller ones.

B

Benefic — Venus and Jupiter, classed in Hellenistic astrology as the planets that help. The opposite of malefic.

Birth chart — a map of the sky as seen from one place at one moment, almost always a birth. Also called a natal chart or radix.

C

Cadent houses — the third, sixth, ninth and twelfth houses. Traditional texts rate them as the weakest positions for a planet.

Cardinal signs — Aries, Cancer, Libra and Capricorn, the signs that begin each season.

Cazimi — a planet within about 17 minutes of arc of the exact degree of the Sun, read traditionally as strengthened rather than damaged.

Chart ruler — the planet that rules the sign on the Ascendant. Both traditional and modern astrology give it unusual weight in reading a chart.

Chiron — a small body between Saturn and Uranus, discovered in 1977. Its interpretation as a "wound" is entirely late twentieth century and has no classical basis.

Combust — a planet within roughly 8.5 degrees of the Sun, read in traditional astrology as weakened. Lilly gives the orb; other sources vary.

Composite chart — a chart built from the midpoints between two people's planets, used to describe a relationship as a third thing. A twentieth-century technique.

Conjunction — two planets at or near the same degree of the zodiac, zero degrees apart.

Cusp — the boundary line of a house, or loosely the boundary between two signs. A planet is in one sign or the other; there is no "born on the cusp" of both.

D

Decan — a ten-degree division of a sign, three per sign. The scheme is Egyptian in origin and each decan carries its own ruler.

Descendant — the degree setting on the western horizon, exactly opposite the Ascendant.

Detriment — a planet in the sign opposite the one it rules, such as Mars in Libra. Traditional astrology reads it as working out of its element.

Dignity — a planet's condition by sign, measured on a fixed scheme: domicile, exaltation, triplicity, term and face. Essential dignity is positional and computable; its interpretation is not.

Dispositor — the ruler of the sign a planet occupies. The Moon in Taurus is disposited by Venus.

Domicile — the sign a planet rules and is strongest in, in the traditional scheme.

E

Eclipse — a new or full Moon occurring close enough to a lunar node for the three bodies to line up. They arrive in seasons roughly every six months.

Ecliptic — the apparent path of the Sun across the sky over a year; the reference circle the zodiac is measured along.

Electional astrology — choosing a time to begin something by the chart of that moment, rather than reading a chart already fixed. The basics are set out in Choosing a date: the basics of electional astrology.

Element — one of four groupings of the signs: fire, earth, air, water. Three signs each.

Ephemeris — a table of planetary positions by date. Modern ones are computed from the same astronomical data used for spacecraft navigation.

Exaltation — a sign in which a planet is held to be honoured, distinct from the sign it rules. The list is fixed and very old; the reasoning behind it is not recorded.

F

Fall — the sign opposite a planet's exaltation.

Fire signs — Aries, Leo and Sagittarius.

Fixed signs — Taurus, Leo, Scorpio and Aquarius, the signs that sit in the middle of each season.

H

Horary astrology — answering a specific question from a chart cast for the moment the question is understood. Lilly's 1647 text is the main source for the English tradition.

House — one of twelve divisions of the chart, tied to the horizon rather than the zodiac, each associated with an area of life.

House system — one of several competing methods for dividing the chart into houses. Whole sign, Placidus and Koch are the most used; they often disagree by a whole house.

I

Imum Coeli — the lowest point of the chart, opposite the Midheaven. Abbreviated IC, sometimes loosely called the nadir.

Ingress — a planet's entry into a new sign.

Inner planets — Mercury, Venus and Mars, the fast-moving bodies whose positions change noticeably within days.

L

Luminaries — the Sun and Moon, grouped apart from the five visible planets in all traditional texts.

Lunation — a new or full Moon.

M

Malefic — Mars and Saturn, classed in Hellenistic astrology as the difficult planets. Modern practice mostly softens the reading; traditional practice does not.

Midheaven — the highest point of the chart, where the ecliptic crosses the meridian. Latin Medium Coeli, abbreviated MC.

Modality — the grouping of signs as cardinal, fixed or mutable. Four signs each.

Mutable signs — Gemini, Virgo, Sagittarius and Pisces, the signs that close each season.

Mutual reception — two planets each sitting in a sign the other rules, read as a working arrangement between them.

N

Nodes — the two points where the Moon's orbit crosses the ecliptic. The north node is where it crosses going north; the south node is opposite. They move backwards through the zodiac, a full cycle in about 18.6 years.

O

Opposition — two planets 180 degrees apart.

Orb — the allowance either side of an exact aspect within which it still counts. There is no agreed standard; astrologers use anything from 3 to 10 degrees depending on the bodies involved.

Outer planets — Uranus, Neptune and Pluto, discovered in 1781, 1846 and 1930. Because they move slowly, whole birth-years share their sign.

P

Part of Fortune — a calculated point, not a body, derived from the Sun, Moon and Ascendant. Hellenistic in origin, and the formula reverses between day and night charts.

Peregrine — a planet with no essential dignity anywhere in the sign it occupies.

Pluto — reclassified by astronomers as a dwarf planet in 2006. Astrologers kept using it; the reclassification is a question of astronomical category, not position.

Profection — a timing technique that advances the chart one house per year of life. Hellenistic and medieval, revived in the last thirty years.

Progression — a symbolic timing technique, most commonly secondary progression, which counts one day after birth as one year of life.

R

Retrograde — the apparent backwards motion of a planet against the stars, caused by the relative motion of Earth and that planet. The motion is apparent, not actual; the appearance is real and calculable.

Return — a chart for the moment a planet comes back to its natal degree. Solar returns are annual; the Saturn return falls near ages 29, 59 and 88.

Rulership — the assignment of each sign to a planet. The traditional scheme uses the seven visible bodies; the modern scheme reassigns Scorpio to Pluto, Aquarius to Uranus and Pisces to Neptune.

S

Sect — the division of charts into day (Sun above the horizon) and night. Sect changes which planets are read as helpful. Central to Hellenistic practice, dropped for centuries, now back in use.

Sextile — two planets 60 degrees apart.

Sidereal zodiac — a zodiac measured against the fixed stars, used in Indian astrology. Currently about 24 degrees offset from the tropical zodiac.

Square — two planets 90 degrees apart.

Stationary — a planet at the turning point between direct and retrograde motion, appearing motionless.

Stellium — three or more planets gathered in one sign or house. A modern term.

sun sign — the sign the Sun occupied at birth, and the only thing a newspaper horoscope uses. It is one placement of many, which is part of why Why your horoscope is sometimes wrong exists.

Synastry — comparing two birth charts by aspect between them. Treated at length in Astrological compatibility: how synastry actually works.

T

Transit — a planet's current position, and its aspects to a birth chart. The positions are astronomy; the reading of them is interpretation.

Trine — two planets 120 degrees apart.

Triplicity — a dignity scheme assigning rulers to each element, differing by day and night. Dorotheus of Sidon, first century AD.

Tropical zodiac — a zodiac measured from the spring equinox rather than the stars. Standard in Western astrology.

V

Void of course — said of the Moon when it will make no further major aspect before leaving its sign. Lilly's definition is looser than the modern one.

W

Water signs — Cancer, Scorpio and Pisces.

Whole sign houses — a house system in which each sign is one house, the rising sign being the first. The Hellenistic default, and back in wide use since the 1990s.

Z

Zodiac — the twelve 30-degree divisions of the ecliptic. The signs share names with constellations but are not the same thing, and have not lined up with them for roughly two thousand years.

Which of these terms do astrologers disagree about?

Four, mainly, and the disagreements are old and unresolved.

Term The disagreement
House system Whole sign, Placidus, Koch, Equal and others give different house placements from the same birth data. No test has settled it.
Rulership Whether Uranus, Neptune and Pluto rule signs. Modern astrology says yes, from the nineteenth century onward. Traditional astrology says no and keeps the seven-planet scheme.
Zodiac Tropical or sidereal. Western practice uses tropical, Indian practice sidereal, and both produce readings their practitioners defend.
Orb How wide an aspect can be and still count. Purely conventional; there is no agreed figure.

Naming the disagreement is more useful than hiding it. A chart drawn two ways is two charts, and a site that tells you otherwise has simplified something it should not have.

Which terms describe something computed and which describe an interpretation?

Everything under positions and angles is computed: sign placements, house cusps once a system is chosen, aspects once an orb is chosen, retrograde stations, eclipse dates, return dates. Those come out of an ephemeris and two astrologers using the same settings will get identical numbers. How we compute our horoscopes sets out the settings used here.

Everything else — benefic and malefic, dignity as strength, what a Mars square Saturn does to a person — is interpretation carried by a tradition, and the traditions differ. The distinction between the two categories is not a technicality. It is the difference between a claim that can be checked and a claim that cannot, and Astrology and science: an honest page deals with what that means for the subject as a whole.

More in Practical