The great circle that passes through the east and west points of the horizon, and the zenith and nadir (points directly overhead and below).

Printable glossary of terms (pdf file)

Where two planets are applying to aspect but before the aspect perfects another planet overtakes the first and perfects an aspect with the second.

This refers to a style of chart wheel, sometimes known as an ‘unequal wheel’. It places the planets and houses against a 360° wheel, allowing the span of each house to be unequal (and therefore having the disadvantage of bunching up collections of planets) but allows aspects to be read with ease. The alternative makes each house the same size and allows an easy identification of a planet’s house position, but aspects between the planets are less easy to identify as zodiacal measurement is distorted.

Immensely influential Roman astronomer, astrologer, geographer and scientist who lived in the vicinity of Alexandria, Egypt. He has been called “the most important single figure in the history of astrology, and one of the most important in the history of astronomy” (Robbins, Intro to the English translation; Loeb, 1940). His astronomical textbook, known as Almagest (from the Arabic phrase Al Majesti, ‘The Greatest’) was revered as the ultimate source of reference for astronomers until the 16^th century. Ptolemy’s astrological textbook, Tetrabiblos (Gk: ‘Four Books’) also became the standard bearer for subsequent generations and was copied, commented on, paraphrased, and translated into many languages. The Tetrabiblos was largely responsible for laying down the basic precepts of astrology during the Arabic and Medieval periods and was a necessary textbook in some of the finest universities of the Renaissance and early modern Europe.

Methods of house division that associate the ascendant with the cusp of the 1st house, the MC with the cusp of the 10th house, the descendant with the cusp of the 7th house and the IC with the cusp of the 4th house, and then seek an equal division (of time or space) within those quadrants. The equal house system is not a quadrant system, and so the MC does not necessarily denote the cusp of the 10th house.

The division of the celestial sphere by the horizon and meridian to give four quarters between each of the four angles.

The person asking the question in a horary chart.

The thing asked about in a horary chart.

The source chart from which derived houses or progressions are obtained. In charts that use ‘turned houses’ (as in horary), references to the ‘radical house’ relate to the normal flow of houses, which ties the 1st house to the ascendant. So the radical 10th house is the normal 10th house of the horary, which falls on the midheaven, although this might be used as the ‘turned 4th house’ for a partner. The term derives from the Latin radix, meaning ‘root’. In traditional texts dealing with natal astrology, the birth chart is also frequently referred to as the ‘radix chart’.