Western astrology employs the tropical zodiac which divides the ecliptic into twelve signs of equal length starting at the first point of Aries, which is defined as the point at which the ecliptic (the apparent path of the Sun through the heavens) crosses the celestial equator at the spring equinox. It is important to note that these signs are completely independent of the astronomical constellations after which they were originally named and no longer bear any relationship to them.
Because the calendar is defined by the movement of the Earth around the Sun, and its orbit is very nearly circular, the sign in which the Sun falls on any day of the year is fairly predictable, though it will vary a little due to the effect of the extra day in leap years. These dates are given in the article that deals with each sign individually. To determine the sign in which the moon and other planets fall on any given day, it is necessary to consult an ephemeris or use an astrological computer program which will have a built-in ephemeris; these computer programs make it quick and easy to calculate the natal chart (also called horoscope) so that the astrologer can spend more time interpreting the chart rather than actually calculating it.
Traditional Rulership versus Modern Rulership
In traditional Western astrology, each sign is ruled by one and only one of the planets (note that in astrology, the Sun and Moon are considered planets, which literally means wanderers, i.e. wanderers among the stars). The traditional rulerships are as follows: Aries (Mars), Taurus (Venus), Gemini (Mercury), Cancer (Moon), Leo (Sun), Virgo (Mercury), Libra (Venus), Scorpio (Mars), Sagittarius (Jupiter), Capricorn (Saturn), Aquarius (Saturn), Pisces (Jupiter).
Many modern, psychologically-oriented astrologers believe that Uranus is the ruler or co-ruler of Aquarius instead of Saturn, Neptune is the ruler or co-ruler of Pisces instead of Jupiter, and that Pluto is the ruler or co-ruler of Scorpio instead of Mars (with other modern astrologers claiming that Pluto rules Aries and not Scorpio). Traditional astrology adheres to the rulerships system listed in the paragraph above, and the debate continues between those who consider the newly discovered planets as rulers or co-rulers of certain signs (modern astrologers) and those that do not (traditional astrologers).
Some astrologers do not even use the astrological signs at all (mostly Cosmobiologists and Uranian Astrologers/Hamburg School); therefore they do not take into account planetary rulerships and the essential dignities when interpreting an astrological chart.
A planet is strengthened (dignified) if it falls within the sign that it rules. If a planet is in the sign opposite that which it rules, it is said to be weakened (detriment).
Each sign is associated with one of the classical elements (fire, earth, air, or water) and one of the four modalities (cardinal, fixed, or mutable). It is also associated with an area of concern: personal, social, or universal.
- Fire signs are associated with intuition, passion, and energy. In combination with the other elements, fire feels that earth will smother it, water will drown it, but air will fan and enliven it.
- Earth signs are associated with sensation, stability, and practicality. In combination with the other elements, earth feels that air will dry it, fire will parch it, but water will refresh and nourish it.
- Air signs are associated with thought and communication. In combination with the other elements, air feels that water will obscure it, earth will suffocate it, but fire will inspire and uplift it.
- Water signs are associated with art and emotion. In combination with the other elements, water feels that fire will make it boil, air will evaporate it, but earth will shape and channel it.
- Cardinal signs are associated with initiation and creativity.
- Fixed signs are associated with stability and determination.
- Mutable signs are associated with resourcefulness and adaptability.
The energies associated with each planet are affected by the sign in which they fall in the following way. (Though due consideration will also be given to other conditions within the astrological chart such as the effect of aspects to other planets, the house in which each planet falls, and the classical element in which the particular sign belongs to)
- Aries (cardinal, fire, personal): assertively, impulsively, head down.
- Taurus (fixed, earth, personal): resourcefully, thoroughly, devotedly, indulgently.
- Gemini (mutable, air, personal): logically, inquisitively, superficially.
- Cancer (cardinal, water, personal): protectively, sensitively, clingingly.
- Leo (fixed, fire, social): generously, proudly, theatrically.
- Virgo (mutable, earth, social): practically, efficiently, critically.
- Libra (cardinal, air, social): co-operatively, fairly, lazily.
- Scorpio (fixed, water, social): passionately, sensitively, anxiously.
- Sagittarius (mutable, fire, universal): freely, straightforwardly, carelessly.
- Capricorn (cardinal, earth, universal): prudently, cautiously, suspiciously.
- Aquarius (fixed, air, universal): democratically, unconventionally, detachedly.
- Pisces (mutable, water, universal): imaginatively, sensitively, distractedly.
Phrases, keywords and concepts associated with each astrological sign
- Aries -- "I want," action oriented, pioneering, assertive, "me" first, enthusiasm, leader, competitive, selfish, head/brain
- Taurus -- "I have," sensual, cautious, acquisitive, musical, traditional, stubborn, throat/neck
- Gemini -- "I think," curious, talkative, sociable, duality, mercurial, whimsical, intelligent, superficial, hands/arms
- Cancer -- "I feel," sensitive, tenacious, family and home oriented, helpful, nurturing, moody, stomach/breasts
- Leo -- "I am," passionate, dramatic, independent, noble, creative, leader, egotistical, heart/back
- Virgo -- "I serve," practical, work and service oriented, critical, common sense, intelligent, health conscious, fussy, intestines/digestion
- Libra -- "We are," partnerships, balance, grace, charm, cooperative, social, ideas, lazy, kidneys/lumbar
- Scorpio -- "I desire," intense, controlling, sexual, compulsive, deep, secretive, mysterious, obsessive, genitals
- Sagittarius -- "I seek," philosophic, fun-loving, adventurous, blundering, wanderlust, scattered, hips/thighs
- Capricorn -- "I build," ambitious, cautious, authoritative, cunning, competent, stable, saturnine, knees/skeleton
- Aquarius -- "I know," friendships, cause-oriented, the group, society, progressive, eccentric, aloof, calves/ankles
- Pisces -- "I believe," feeling, duality, spirituality, soul growth, suffering, artistic, overly emotional, feet
- Rulerships (http://www.skyscript.co.uk/rulership.html) - This site deals with the traditional rulership system as used in Classical Astrology.
- Ptolemaic Dignities (http://www.skyscript.co.uk/essential_dignities.html) - Ptolemy's table of Essential Dignities.
- Horary Rulership (http://www.skyscript.co.uk/horary1b.html) - Learn more about the rulership system as it applies to horary astrology.