Richard Dunn

Astrology is a complex art with its own vocabulary and a number of different traditions. These have changed over time. This glossary covers the key astrological and related terms mentioned in this volume. It is intended primarily to give sufficient explanation to aid understanding of the individual chapters. For those wishing to explore the terminology further, the major sources consulted are listed at the end of the glossary.

accidental dignity

see dignity.


a book or set of tables, usually containing a calendar, with astronomical data and calculations, ecclesiastical and other anniversaries and other information, including astrological and meteorological forecasts.


a circle on the celestial sphere parallel to the horizon; a parallel of altitude.


the most influential planet (as determined by the dignities of each) in a chart.

application / applying

see aspect.


the degree of the zodiac rising over the eastern horizon at the time for which an astrological figure or chart is cast; often also applied to the whole sign rising.


an astrologically significant angular relationship (measured from the Earth’s centre) between two or more planets or nodal points in a chart (see Table G1). Each aspect operates fully when the angle is exact, but has a partial influence for as long as part of the orb of each planet maintains the appropriate angle. In this case, the faster moving planet is said to be applying as it approaches the aspect with the other planet or nodal point, separating as it moves away. Traditionally, an aspect is more powerful during application than separation. Ptolemaic astrology used five aspects, to which Johannes Kepler (1571–1630) added a further eight.

TABLE G1Planetary aspects; based on Nicholas Campion, The Practical Astrologer, Twickenham, Hamlyn Publishing, 1987, p. 70, and Deborah Houlding, “Glossary of terms”, (accessed 13 November 2015)TABLE G1

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an aide-mémoire depicting the aspects between the planets.

astronomical hours

see equal hours.

azimene (or lame)

see degrees.

Babylonian hours

see equal hours.

Bohemian hours

see equal hours.

Caput Draconis or head of the dragon

the north (or ascending) node of the Moon, where it crosses the ecliptic; the most powerful nodal point in the chart, favourable for affairs governed by the house in which it is located; see also Cauda Draconis.

cardinal houses / signs or cardines

the houses (first, fourth, seventh and tenth) or signs (Aries, Cancer, Libra, Capricorn) falling on the cardinal angles.

casting the rays

According to ancient Greek astrology each planet casts seven rays of influence to other points of the ecliptic. The rays are defined by reference to a hexagon, square and equilateral triangle. In the simplest method, the polygons are inscribed in the ecliptic with one apex at the planet’s position. For interpretation, the theory of rays and aspects between the planets was often related to the theory of the aspects between the signs. Thus the trine ray or aspect was regarded as beneficial, the sextile as less beneficial, the quartile as harmful, and opinions differed as to the qualities of the opposite ray and aspect. Medieval Islamic astrologers enthusiastically adopted the theory of the seven rays.

Cauda Draconis or tail of the dragon

the south (or descending) node of the Moon, where it crosses the ecliptic; regarded as an unfavourable influence for affairs governed by the house in which it is located; see also Caput Draconis.

celestial sphere

an imaginary sphere, with Earth at its centre, on which all other celestial objects are considered to lie.


the astrological diagram drawn for a specific time (Fig. G1), showing the positions in the heavens of the planets, luminaries, nodal points and cusps of the houses; synonymous with figure and, in modern usage, horoscope. See also division, house.


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Astrological chart for the birth of Andreas Vesalius on 30 December 1514; from Girolamo Cardano, Libelli quinque, Nuremberg, Joannes Petreius, 1547, fol. 178 (Wellcome Library, London).


a transliteration of a Greek term used to refer to a planet activated in a chart for a certain timespan; literally meaning “lord of time” because the planet is activated as a lord or ruler in the chart for a specific period.


see aspects.

crisis / critical day

the theory of critical days links the course of an illness to the Moon’s phases, with crises or critical days at each quarter of the Moon’s cycle (i.e. every seven days), at which time the patient might improve or get worse.


the beginning or entrance of a house or sign; see also division.


see dignity.


a 10° division of each sign into first, second and third decan, each ruled by a specific planet; also called face.


individual degrees of the zodiac may have particular characteristics that come into play when any of the planets or nodal points are found there. In particular, they may influence the physical or mental characteristics of the subject of a nativity if the ascendant or its lord, or possibly the Moon, is found in one of them. They can have a similar interpretation in horary astrology. The most common characteristics are:

  • masculine or feminine—helpful in determining the sex of a thief or unborn child, for example;

  • lucid (or light), dark, smoky or empty (or void);

  • pitted (or deep), indicating either something of the subject’s complexion or that a querent may need help if they are to improve their condition;

  • lame (or deficient or azimene)—perhaps referring to the subject, but also regarded as debilitating when on the ascendant or otherwise prominent in the chart (e.g. with the Moon in that degree).

  • increasing fortune—indicating that the querent will gain riches.


a planet is said to be in depression when it is in the sign or degree opposite its exaltation; also called fall; see also debility, dignity.


strictly speaking, the cusp of the seventh house (i.e. the degree of the zodiac setting below the western horizon), but sometimes also used to refer to the whole seventh house.


a planet is in detriment when it is in the sign opposite its own domicile.


the situation of a planet in which its influence is heightened due to its position in the zodiac, the aspects it has with other planets or nodal points, or its relationship to the houses. Essential dignities occur when a planet is:

  • in its domicile or in mutual reception by domicile;

  • in exaltation or in mutual reception by exaltation;

  • in its own triplicity;

  • in its own term;

  • in its own face.

Accidental dignities derive from other relationships (e.g. with the houses). Essential and accidental dignities may come into play at the same time. The opposite of dignity is debility, a relationship that in general weakens the influence of the planet. The essential debilities include a planet being in detriment and in depression.


the study of future configurations of the planets and angles in relation to a radical chart (i.e. a chart at a key moment such as a person’s birth or the beginning of an event or action) in order to understand the future course of events; also known as progression.


the method of defining the cusps or boundaries of the houses in a chart. Many different methods have been devised over the centuries, often named after practitioners. The more important methods include:

  • equal-house (sometimes called Ptolemaic) method—the ecliptic is divided into twelve equal divisions of 30°, starting from the degree of the ascendant, which acts as the cusp of the first house.

  • Regiomontanus or equatorial fixed-boundary method, also called rational—the celestial equator is divided equally into twelve, with the divisions projected onto the ecliptic along great circles that take in the north and south points on the horizon; each house spans 30°. Though attributed to Regiomontanus (Hans Müller of Königsberg, 1436–1476), the method can be traced back to at least the eleventh century and was the main European method for several centuries, being employed by prominent seventeenth-century astrologers including William Lilly (1602–1681).

  • Campanus method—the prime vertical is divided equally into twelve, with the divisions projected onto the ecliptic along great circles that take in the north and south points on the horizon. Although attributed to Johannes Campanus (c. 1220–1296), the method is known to have been used by Al-Bīrūnī (b. 973).

  • Alcabitius, common or standard method—the parallel of declination on which the ascendant is located is divided equally from the ascendant, using lines of constant right ascension to project the house cusps onto the ecliptic.

  • Porphyry method—each quadrant of the ecliptic is divided into three equal parts. This is the oldest system of quadrant-style house division. Although later attributed to Porphyry of Tyre (c. 234–c. 305), it had already been described by the second-century astrologer Vettius Valens (120–c. 175).

  • Placidus or hour-line method—the paths drawn for each degree of the ecliptic to move from the Imum Coeli to the horizon, and from the horizon to the Medium Coeli, are trisected to define the cusps of houses 2, 3, 11 and 12. The cusps of houses 8, 9, 5 and 6 are opposite these. The system was named after the Italian Benedictine monk, Placidus de Titis (Placido de Titi, 1603–1668), who popularized its use during the seventeenth century, although it had been described earlier.

domicile or mansion

the sign ruled by a specific planet (see Table G3). When a planet is in its domicile, which is an essential dignity, its influence is enhanced; see also dignity, sign.


the great circle that is the apparent path of the Sun among the constellations in the course of a year.

election / electional astrology

a form of casting and interpreting a chart in order to determine the best time for commencing a particular action or endeavour; for example, marriage, a journey or a law suit.

ephemeris / ephemerides

a set of tables listing the positions of the planets and nodal points and other astronomical data.

equal hours or equinoctial hours

the time system by which each whole day is divided into 24 equal parts. Typically, the day was divided either into 24 equal hours beginning at midnight or two twelve-hour periods beginning at midnight and noon. In the first case the hours were referred to as “large” or “great” hours; in the latter case they were “small”, “common”, “ordinary”, “German” or “French” hours. Three additional systems based on “large” hours were common in the Renaissance and early modern period: “Italian”, “Bohemian” or “foreign” hours, reckoned from sunset; “Babylonian” or “Greek” hours, reckoned from sunrise; and “Nuremberg” hours, which counted daylight hours by the Babylonian system and night hours by the Italian system. The system of “astronomical hours”, which was also based on equal hours, reckoned the day from noon to noon. See also unequal hours.


an instrument for finding the positions of the planets using a geometrical model to represent the position of the bodies in question.

essential dignity

see dignity.


a specific degree, or sometimes a sign, of the zodiac in which a planet exerts its most powerful influence. The opposite of exaltation is fall or depression. See also dignity.


see decan.


see depression.


a synonym for chart.

French hours

see equal hours.


the practice of calculating and making predictions from a chart for the moment of birth.


the chart drawn for a person based on his/her time of birth; also called a nativity or horoscope.

German hours

see equal hours.

head of the dragon

see Caput Draconis.


a seven-day cycle in which each day corresponds to one of the seven planets, with the first day being Saturday (Saturn).

horary / horary astrology

the art of making a forecast regarding a specific question from a chart or figure drawn for the moment the question is asked.


the circle around the Earth separating the hemisphere visible to the observer (or querent) from the hemisphere that is invisible. The eastern horizon is the degree rising in the east.


until the eighteenth century, horoscope referred to the ascendant degree in the chart; in modern usage, it is synonymous with chart.


see equal hours, unequal hours.


the division of the sky into a number of regions (typically twelve, although some systems use other numbers) for the purpose of creating a chart, usually beginning with the first house at the rising horizon. Each house governs a different area of life (Fig. G2).


medical astrology.


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The houses of the traditional chart showing the areas of life they govern.

Imum Coeli

the point opposite the Medium Coeli (mid-heaven), also known as the anti-mid-heaven; usually the cusp of the fourth house.

Italian hours

see equal hours.

judicial astrology

a form of astrology seeking to make predictions about small-scale phenomena, particularly including the futures of individuals based on their geniture.


a term for the Sun and Moon; the term luminary can also be used.


see terms.


properly applied, the most powerful planet in a chart.

lord of time

the planet ruling a particular hour of the day; also called chronocrator or planetary ruler; see also planetary hours.

lord of the triplicity

see tripicity.

lower mid-heaven

a variant term for Imum Coeli.


see light.

lunar mansion

a division of the path of the Moon into equal arcs, often 27 or 28 segments, each containing a specific asterism (group of stars). Each mansion has a name and specific interpretation, affecting how a planet in that mansion exerts its influence. Lunar mansions were used in the Islamic world as a merger of pre-Islamic and Indian systems, and were then introduced into Europe during the Middle Ages.

lunar nodes

see Cauda Draconis and Caput Draconis.


see domicile.

Medium Coeli

a term properly applied to the culminating degree of the ecliptic (the point of the ecliptic on the meridian); also known as mid-heaven or upper mid-heaven.

melothesia or melothesic man

see Zodiac Man.


the plane containing the observer/querent and both celestial poles, or containing the observer, the zenith and a pole; more colloquially, the north-south line at a particular position on Earth.


see Medium Coeli.

mundane astrology

a form of astrological prediction limited to forecasts of trends over large regions or populations.

mutual reception

in principle, mutual reception occurs when each of two planets is in a dignity of the other. In practice, only mutual reception between domicile and exaltation are considered significant.


see geniture.

nodal point

any astrologically sensitive degree on the ecliptic; see Caput Draconis, Cauda Draconis, Part of Fortune.

Nuremberg hours

see equal hours.


see aspect.


see aspect.

orb or orbes planetarum

the area of influence within which planets in aspect are said to exert an influence while applying or separating. In some cases, the aspect itself can be ascribed an orb.

Part of Fortune

a nodal point in the chart that is the same distance of zodiacal arc from the ascendant as the Moon is from the Sun (according to one of the methods for calculating it), marking the point where the Moon would be at the time of symbolic sunrise; held to be beneficial for the affairs governed by the house in which it is situated.

planetary hours

each hour of the day is said to be ruled by one of the planets (Table G2), a cycle that gives rise to the names of the days of the week (from the planet ruling the first hour). This sequence is noticeable in the names of the days of the week in Romanesque languages; for example, Martedì (Tuesday) from Marte (Mars), Mercoledì (Wednesday) from Mercurio (Mercury), Giovedì (Thursday) from Giove (Jupiter) and Venerdì (Friday) from Venere (Venus) in Italian. It is also apparent in some English names (notably Saturday, Sunday and Monday), but less so in others. Friday, for instance, comes from the Old English Frīġedæġ (day of Frigg), reflecting the association of the English goddess Frigg with the Roman goddess Venus.

TABLE G2The planetary hours of the day and nightTABLE G2

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planetary ruler

each planet is held to rule over a particular sign or signs (Table G3).

TABLE G3The planetary rulers according to Ptolemaic astrologyTABLE G3

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for traditional astrological purposes (and for all purposes until the eighteenth century), the seven celestial bodies seen to be moving against the background of the fixed stars: Sun ( ☉ ); Moon ( ☽ ); Mercury ( ☿ ); Venus ( ♀ ); Mars ( ♂ ); Jupiter ( ♃ ); Saturn ( ♄ ). Each planet exerts a distinctive influence.

prime vertical

the great circle taking in the zenith and east and west points on the observer’s or querent’s horizon.


see direction.


that which promises fulfilment, generally meaning a planet that will form a particular aspect through progression or direction.


this can mean the qualities (hot, cold, humid and dry) of the four elements. Thus air is hot and humid, earth is cold and dry, fire is hot and dry, and water is cold and humid. It can also refer to the three qualities (cardinality, fixity and mutability), by means of which each of the four elements finds expression in the signs of the zodiac. Aries, Cancer and Libra, for example, are of the cardinal quality.


see aspect.


the person who asks a question in horary astrology.


used in traditional texts as a synonym for influence; see also casting the rays.


used to describe a planet when it appears (from Earth) to be moving backwards in the zodiac, generally held to have a negative connotation for the planetary influence.

revolution(s) of the years

an astrological technique in which the chart is progressed to the future point or points at which the Sun has returned to the same place in the zodiac (e.g. the place it was first in at the time of a person’s birth), used for assessing issues that will arise over the period.


see planetary ruler

seasonal hours

see unequal hours.

separation / separating

see aspect.


see aspect.


one of the 30° arcs of the zodiac, through one of which the Sun passes each month. The signs are named after the twelve constellations with which they coincided at a former epoch. The signs are grouped into four groups called triplicities or trigons, each of which is associated with one of the four elements (fire, air, water, earth; see Table G4).

Spanish hours

see equal hours.


see aspect.

tail of the dragon

see Cauda Draconis.


irregular divisions of the signs, generally into five segments, each falling under the influence of one of Mercury, Venus, Mars, Jupiter or Saturn; also known as limits. Girolamo Cardano (1501–1576) devised a system of seven terms, each ruled by one of the seven planets.


see triplicity.


see aspect.

triplicity or trigon

a group of three signs, each separated by 120°. Each triplicity is linked with one of the elements, has a planetary ruler (or lord) by day, another by night, and a third known as a companion (Table G4).

TABLE G4The triplicities and their rulersTABLE G4

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unequal hours

the system in which the periods of daylight and darkness are each divided into twelve equal intervals, with the hours counted from sunrise and sunset. This was the most common system used for counting hours in medieval and Renaissance Europe. Noon is defined as the moment when the Sun reaches its greatest altitude and marks the midpoint of the daylight period; sunrise and sunset occur six hours earlier and later. The lengths of each daytime hour and night-time hour are unequal (except at the spring and autumn equinoxes and on the equator) and vary according to geographical latitude and date. Unequal hours can also be known as temporal, seasonal, Jewish or planetary hours. See also equal hours.

upper mid-heaven

a variant term for Medium Coeli.


a device that rotates, usually referring to one or more discs which turn within a circular scale.


the point on the celestial sphere directly above the observer or querent.


an astronomical text with tables compiled in the Islamic world.


the belt of the celestial sphere extending about 8 or 9° on each side of the ecliptic, within which the apparent motions of the planets take place. The zodiac is usually divided into twelve equal signs.

Zodiac Man

the image of a human linked with the twelve zodiacal signs, indicating which signs rule which parts of the body (Fig. G3); also called melothesia or melothesic man.


Download Figure

Zodiac Man; from Kalendar Deutsch, Augsburg, J. Blaubiren, c. 1483 (Wellcome Library, London).

  • Silke Ackermann, “Astrological Scales on the National Maritime Museum Astrolabes”, in Koenraad Van Cleempoel, Astrolabes at Greenwich, Oxford and London, Oxford University Press/National Maritime Museum, 2005, pp. 73–89.

  • The Astrology Dictionary, (accessed 23 March 2017).

  • Nicholas Campion, The Practical Astrologer, Twickenham, Hamlyn Publishing, 1987.

  • J. Casulleras, J.P. Hogendijk, “Progressions, Rays and Houses in Medieval Islamic Astrology: A Mathematical Classification”, Suhayl 11 (2012), pp. 33–102.

  • EPACT, (accessed 15 June 2017).

  • Deborah Houlding, “Glossary of Traditional Astrological Terms”, Skyscript, (accessed 15 June 2017).

  • Deborah Houlding, “The Problems of House Division”, Skyscript, (accessed 15 June 2017).

  • Fred Gettings, Dictionary of Astrology, London, Routledge & Kegan Paul, 1985.

  • Annabella Kitson (ed.), History and Astrology: Clio and Urania Confer, London, Unwin Hyman, 1989, pp. 253–257.

  • Medieval Astrology Guide, (accessed 25 September 2017).

  • John D. North, Horoscopes and History, London, Warburg Institute, 1986.

  • OED Online, (accessed 23 March 2017).

  • Renaissance Astrology, (accessed 22 June 2017).

  • James Wilson, A Complete Dictionary of Astrology, London, William Hughes, 1819.

Heaven and Earth United

Instruments in Astrological Contexts


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