Astrology Glossary

Glass Zodiac

A handy glossary of the main terms used in the study of astrology:

Acceleration on the Interval

A technique for adjusting the birth chart in relation to sidereal time which runs about 4 minutes faster than Greenwich Mean Time, or clock time.


The four angles of the birth chart which form a cross, with the Ascendant and the Descendant on the horizontal, and the Midheaven (MC) and the Imum Coeli (IC) on the vertical.


A house in the birth chart which is found at one of the angles. Angular houses are the 1st, 4th, 7th, and 10th.

Apparent Motion 

Refers to the fact that the Sun doesn’t really rise – the Earth turns so it appears that the Sun rises. Also, the Sun doesn’t move through the signs of the zodiac. The Earth moves around the Sun which is stationary, and this causes the appearance that the Sun is moving through the signs. The motion is apparent, not real.


Relates to aspects where the two planets are not quite forming an exact aspect yet, but soon will.


Any part of a circle as measured around its circumference.


The degree of the zodiac seen rising on the eastern horizon at the moment of birth at a particular latitude. Each degree takes about four minutes to rise, depending upon how far away from the equator you are. See Ascension.

Ascension, long and short

The ecliptic and the equator aren’t parallel so some signs rise more quickly than others. In theory, each sign takes 2 hours to rise, but in reality it varies according to latitude. The higher the latitude in the northern hemisphere, the shorter the ascension. In the southern hemisphere, long and short ascension are reversed.


Two planets are considered to be in aspect to each other when there are a specific number of degrees between them, measured around the circumference of the chart. See individual entries for aspect types, also Orb.


Astrology is not a science. It’s a symbolic language and system for interpreting the correlation of the movement of the planets with human experience.


The science of studying the movement of the planets and stars in relation to their physical nature.

Birth Chart

A circular diagram (square in Jyotish astrology) that gives the exact position of the planets and angles at the time of birth for a specific location.


A house in the birth chart which precedes an angular house (or follows a succedent house). Cadent houses are the 3rd, 6th, 9th, and 12th.

Chart Rectification

Refers to techniques used to correct a possibly uncertain birth time by studying the individual’s characteristics and the events in their life according to transits and progressions over the chart.

Chart Ruler

This is the planet that rules the sign found on the Ascendant and is sometimes called the Lord of the Horoscope.

Chart Shape

This describes how the planets are laid out in the birth chart and consists of various patterns which influence how the planets interact.


A planet is ‘combust’ when it is placed very close to the Sun in the birth chart. Traditional astrology considers this a sign that the planet has lost some of its force.


A major aspect. Planets are conjunct when they are found at the same, or almost the same, degree in a sign.


Clusters of stars which appear to form particular shapes. The 12 that became important for astrology gave their names to the 12 signs of the zodiac. Note: the zodiac and the constellations are not the same thing! See Zodiac.


This is the line dividing one sign from another, or one house from another in a birth chart. The cusp of the first house is called the Ascendant and the rest follow around from there in a counter-clockwise direction.

Decan / Decante

Each sign is 30 degrees of the full circle. Each 30 degree segment is subdivided into another three 10 degree segments called decans. These have their own sub-rulers which alter the meaning of placements in those locations.


The distance of a planet north or south of the celestial equator. The celestial equator is the Earth’s equator projected into space.


This is the planet that rules the sign in which another planet is placed. For example, when Mercury is in Cancer, the depositor is the Moon, because the Moon rules Cancer.


The point in the birth chart directly opposite the Ascendant. This is the sign which is setting in the west at the moment of birth.


A planet is considered in detriment (or badly placed) when it’s found in the sign opposite the one it rules, according to traditional astrology. For example, Mars rules Aries so is in detriment in Libra.


Part of the retrograde cycle when a planet has stopped appearing to move backwards and is now moving forwards again. When the retrograde motion ends the planet is described as going direct.


This is an imaginary line through space which is formed by the apparent motion of the Sun around the Earth. It is the ecliptic which forms the zodiac.


Sometimes called the Triplicities. The elements are made up of three groups of four signs known as Fire, Earth, Air, and Water. The Fire signs are Aries, Leo, and Sagittarius. The Earth signs are Taurus, Virgo, and Capricorn. The Air signs are Gemini, Libra, and Aquarius. The Water signs are Cancer, Scorpio, and Pisces.


Any planet positioned close to the Midheaven is said to be elevated. In astronomy, the elevation marks the distance of a planet above the horizon, or its altitude.


This is a table of planetary positions which show the precise daily position of all the planets and the Sun, either at noon or midday.


The imaginary line drawn around the middle of the Earth which divides the planet into northern and southern hemispheres. This line can be extended into space where it is called the celestial equator.


Some planets are considered to be exulted, or well-placed in certain signs, according to traditional astrology. For example, the Sun is exulted in Aries.


When a planet that is exulted in a particular sign is found in the opposite sign, it is considered to be in fall, or weakly placed, according to traditional astrology. For example, since the Sun is exulted in Aries, it is thought to be weak in Libra.


This word is used to refer to predictive astrology to show that the future is not fixed or predictable. Possible events can only be forecast or estimated in a similar way to the weather.

Grand Cross

A cross formed in a birth chart by four planets which are arranged in two oppositions set at right angles, so the planets are all 90 degrees from each other.

Grand Trine

A triangle formed in a birth chart by three planets which are 120 degrees from each other.

Greenwich Mean Time

Or GMT. The mean solar time as measured at the Greenwich meridian, or prime meridian, which is at 0 degrees longitude.


In a birth chart, the hemispheres refer to the upper and lower parts of the chart.


The birth chart diagram, sometimes called a Natal Chart. The word ‘horoscope’ is often used to describe what passes for astrology in newspapers and on some online sites, where predictions are made based on sun signs. This is not astrology!


The division of the birth chart into 12 sections. The houses don’t necessarily correspond with the 12 divisions of the zodiac. There are many different systems for calculating the house positions, such as the Equal House System, the Placidus System, and the Koch System.

House Ruler

Each house is ruled by the planet that rules the sign found on the cusp of the house. For example, if Aries is on the cusp of the 3rd house, then the 3rd house is ruled by Mars, even if Mars is placed elsewhere in the chart.

Imum Coeli (IC)

One of the angles of the birth chart. Imum Coeli means ‘bottom of the sky.’ The IC is the meridian point directly opposite the Midheaven (MC).


A minor aspect. Also known as Quincunx. Planets are inconjunct when they are found 150 degrees apart.

Inner Planets

These are also called the Personal Planets and include all planets up to Saturn. The inner planets are the Sun, Moon, Mercury, Venus, Mars, Jupiter and Saturn.


The distance of a place, either north or south, from the equator.


The distance of a place, either east or west, from the Greenwich meridian.


The traditional name for the Sun and the Moon. Also sometimes called The Lights. Even though the Sun and the Moon are not technically planets, they are considered as planets for the purposes of astrology.


A circle of longitude that passes through a particular place on the Earth. Astrology is concerned with the meridian at Greenwich and calculates the birth chart by determining how far from the Greenwich meridian the birth took place.

Midheaven (MC)

One of the angles of the birth chart. The Midheaven is also known as the Medium Coeli (‘middle of the sky’) and it marks the meridian of the birth place.


This marks the exact midpoint between two particular planets in the birth chart, or between angles, or house cusps.

Moon Nodes

The North and South Nodes of the Moon are the points on the ecliptic where the Moon crosses as it moves either north or south.

Mutual Reception

Planets are considered to be in mutual reception when they occupy the sign ruled by the other. For example: Mars in Libra and Venus in Aries.


Two points (north and south) where a planet’s orbit intersects the imaginary line of the ecliptic. All planets have nodes, but usually only the Moon’s Nodes are used in horoscopes.

Noon Date

One of the techniques used in progressions to calculate when the progressed positions of the planets will apply.


A major aspect. Planets are in opposition when they are found 180 degrees apart.


This is the range of influence for a planet or house cusp. The size of the orb depends upon the planet and the type of aspect, and can range from 2 or 3 degrees to 8 or 9 degrees.

Outer Planets 

The outer planets are those found beyond the orbit of Saturn. These are Uranus, Neptune, and Pluto. Also sometimes called Transpersonal Planets.

Personal Planets

These are the planets used by Traditional astrology and include all the planets up to Saturn, plus the Sun and the Moon. There are seven in total: Sun, Moon, Mercury, Venus, Mars, Jupiter, and Saturn.

Planetary Cycles

Each planet takes a different length of time to move through one orbit of the sun. One revolution equals one cycle, and as they move, they form aspects to each other and to the birth chart in predictable cycles.


The polarity point of a planet is found directly opposite. Each pair of polar signs has a complementary relationship with its opposite in the zodiac: Aries with Libra, Taurus with Scorpio, Gemini with Sagittarius, Cancer with Capricorn, Leo with Aquarius, and Virgo with Pisces.

Precession of the Equinoxes

The slow retrograde movement of the equinox point along the line of the ecliptic which is caused by the wobble of the Earth as it revolves. It takes about 26,000 years to complete a full circle, called a Great Year.


One of the techniques used in forecasting with the birth chart where the chart is ‘progressed’ into future periods. There are various methods, including Solar Arc and ‘a day for a year’.


Sometimes called the Quadruplicities. The Qualities are made up of three groups of four signs known as Cardinal, Fixed, and Mutable. Cardinal signs are Aries, Cancer, Libra, and Capricorn. Fixed signs are Taurus, Leo, Scorpio, and Aquarius. Mutable signs are Gemini, Virgo, Sagittarius, and Pisces.


A minor aspect. Also known as Inconjunct. Planets are quincunx when they are found 150 degrees apart.


A planet is said to be retrograde when it appears to be moving backwards against the zodiac as seen from the Earth. There are also times during the retrograde cycle when a planet will appear to stand still, and then they’re called Stationary.

Rising Sign

Another name for the Ascendant.

Ruling Planet

Signs are ruled by different planets according to their archetypal pattern. The trans-Saturnian planets have been added to the rulership system so some signs have two rulers, the traditional ruler and a new one. For example, Scorpio is ruled by Mars and Pluto.

Secondary Progression

Another name for a type of progression called ‘a day for a year.’


A minor aspect. Planets are semi-sextile when they are found 30 degrees apart. Basically, half a sextile.


A minor aspect. Planets are semi-square when they are found 45 degrees apart. Basically, half a square.


Relates to aspects where two planets have been forming an exact aspect but no longer do and are moving away from each other.


A minor aspect. Planets are sesquequadrate when they are found 135 degrees apart. Basically, a square plus a semi-square.


A major aspect. Planets are sextile when they are found 60 degrees apart.

Sidereal Time

This is time reckoned by the motion of the Earth (or any planet) in relation to the fixed stars, instead of the Sun.

Sidereal Zodiac

This zodiac divides the ecliptic into 12 signs which are named after the constellations. The signs are defined in relation to the fixed stars and deals with the position of the Earth relative to the stars and the celestial sphere. See Tropical Zodiac


An unaspected planet.

Solar Arc

A method of progressing a birth chart by calculating the distance in degrees (the arc) between the progressed Sun and the natal Sun, and then adding that distance to the rest of the planets to create a progressed chart.


A major aspect. Planets are square when they are found 90 degrees apart.


A collection of planets in one part of the birth chart, also sometimes called a multiple conjunction.


A house in the birth chart which follows an angular house (or precedes a cadent house). Succedent houses are 2nd, 5th, 8th, and 11th.

Sun Sign Astrology

This is the type of ‘astrology’ used in newspaper columns and on some online sites to make predictions for each sign of the zodiac. They are based on solar charts which place the Sun in the first house regardless of where your Sun falls in your actual birth chart. This is why Sun Sign Astrology is largely useless and isn’t really astrology.

Tables of Houses

These are tables which show the degrees of signs that occupy the cusp of the houses in different latitudes according to the various house systems.


The movement of the planets through the signs and houses in a birth chart as they relate to the natal planets.

Transpersonal Planets

The transpersonal planets are those found beyond the orbit of Saturn. These are Uranus, Neptune, and Pluto. Also sometimes called Outer Planets.


A major aspect. Planets are trine when they are found 120 degrees apart.

Tropical Zodiac 

The zodiac used by Western astrology divides the ecliptic into 12 signs that are named after the constellations. The signs are defined based on the position of the spring equinox (when the ecliptic intersects with the celestial equator). But due to precession of the equinoxes, this zodiac has drifted away from the sidereal zodiac so they don’t match.


A planetary configuration formed by three planets where two are opposite each other and the third is at a right angle to make a T shape.


A planetary configuration formed by three planets where two are sextile each other and both make a quincunx to the third planet.


This refers to the circle that the sun appears to take as it moves through the sky within a band about 20 degrees wide. The ecliptic runs through the centre of this band and is divided into 12 sections of 30 degrees each. The Sun takes about a month to move through each section, which have been named after the 12 constellations that are visible in that area of the sky. The signs of the zodiac may once have matched the constellations behind them, but due to precession, they no longer do so. Some think that this means astrology doesn’t make sense, but they fail to realise that it’s the ecliptic itself that seen as the zodiac, not the constellations.

Missing words? If there’s a term you’d like to see included in this list, add it to the comments below – and I’ll see what I can do…