Thursday, 8 December 2022, 12:33 AM
Site: School of Traditional Astrology
Course: School of Traditional Astrology (STA Course Portal)
Glossary: Glossary of terms


The degree of the ecliptic (zodiac) that meets the western horizon, and which denotes the 7th house cusp. So called because planets at this point descend beneath the horizon and are no longer visible to the naked eye.


A planet in detriment is in a sign opposite its sign of rulership. This is considered a debility or weakness for the planet.

Diagram showing detriment


Diagram showing dexter and sinister aspects.

Dexter literally means ‘of the right’ and refers to something on the right hand side; sinister means ‘of the left’ and refers to something on the left hand side. According to Pythagorean principles, movement towards the right is more natural and direct than movement towards the left (hence the term ‘righteous’ or the negative undertones given to the word ‘sinister’ generally). This partly recognises the influence of diurnal motion (by which planets move from left to right), and the fact that in any cycle between two planets, the faster moving planet will cast its aspect to the other on the right hand side whilst the cycle is waxing (suggesting growth and vigour), and to the left hand side when the cycle is waning (suggesting retirement and weakness). A ‘dexter aspect’ is therefore said to be more forceful and effective than a sinister one. Dexter aspects are formed in keeping with diurnal revolution (for example, a planet in Pisces applying to a sextile of a planet in Capricorn); sinister aspects are formed against diurnal revolution (for example, a planet in Pisces making a sextile to a planet in Taurus).

Dignities & debilities

Factors that increase a planet’s strength are called dignities; those that weaken it, debilities. These are termed ‘essential’ when they rely upon zodiacal position; and ‘accidental’ if they rely upon anything else. Thus the advantage offered to a planet by being in its own sign or exaltation is an essential dignity, the disadvantage of being in its sign of detriment or fall is an essential debility; but combustion, aspectual connections and matters of angularity or house position are accidental dignities or debilities.


The overall condition, influence, or virtue of a planet once all matters of dignity and debility have been judged. To commit disposition means to pass influence to another planet by aspect or reception.


A planet which rules another because the other is in one of its areas of essential dignity. For example, Venus, the planetary ruler of Taurus, is the dispositor of any planet in Taurus: that planet is said to be diposed by Venus by sign. Planets can also be disposed by the lesser dignities (see essential dignity). The general condition of the dispositor has some bearing on the strength of the planet disposed by it.

Diurnal hemisphere

This is the hemisphere above the horizon, comprising the 7th, 8th, 9th, 10th, 11th and 12th houses.

Diurnal motion/revolution

Apparent motion of the heavens which carries planets from the eastern horizon, up to the midheaven, and down towards the west, as perceived by the senses from our seemingly stationary viewpoint. Also known as ‘primary motion’.

primary v secondary motion

Diurnal sect

See ‘sect’.


Diurnal means ‘of the quality of the day’; nocturnal means ‘of the quality of the night’. Diurnal energies relate to masculinity and the solar principle, being active, direct and expressive, whilst nocturnal energies relate to femininity and the lunar principle, being responsive, indirect, and impressive. Yin and Yang are analogous oriental terms. The characteristics of diurnal and nocturnal influences infiltrate many areas of astrological philosophy, from the alternation of the signs (usually referred to as masculine and feminine), to the assignation of planetary rulerships over the signs. Apart from the Sun and Moon each planet has two rulerships – one diurnal, one nocturnal – to recognise their expression in these altered states (for example, Mars rules Aries, its diurnal ‘house’, and Scorpio, its nocturnal ‘house’).