The zodiac is the belt or band of constellations through which the Sun, Moon, and planets move on their journey across the sky. Astrologers noted these constellations and so attached a particular significance to them. Over time they developed the system of twelve astrological signs of the zodiac, based on twelve of the constellations through which the sun passes throughout the year, those constellations that are “Enlightened by the mind”. Most western astrologers use the tropical zodiac beginning with the sign of Aries at the Northern hemisphere Vernal Equinox always on or around March 21 of each year. The Western Zodiac is drawn based on the Earth’s relationship to fixed, designated positions in the sky, and the Earth’s seasons. The Sidereal Zodiac is drawn based on the Earth’s position in relation to the constellations, and follows their movements in the sky. Due to a phenomenon called precession of the equinoxes (where the Earth’s axis slowly rotates like a spinning top in a 25,700 year cycle), there is a slow shift in the correspondence between Earth’s seasons (and calendar) and the constellations of the zodiac. Thus, the tropical zodiac corresponds with the position of the earth in relation to fixed positions the sky (Western Astrology), while the sidereal zodiac is drawn based on the position in relation to the constellations (sidereal zodiac).
The Twelve Signs In modern Western astrology the signs of the zodiac are believed to represent twelve basic personality types or characteristic modes of expression. The twelve signs are divided into four elements: fire, earth, air and water. Fire and air signs are considered masculine, while water and earth signs are considered feminine. The twelve signs are also divided into three qualities: Cardinal, mutable and fixed.
Aries (The Ram) March 21 to April 20.
Taurus (The Bull) April 21 to May 20.
Gemini (The Twins) May 21 to June 21.
Cancer (The Crab) June 22 to July 22.
Leo (The Lion) July 23 to August 22.
Virgo (The Virgin) August 23 to September 22.
Libra (The Scales) September 23 to October 22.
Scorpio (The Scorpion) October 23 to November 22.
Sagittarius (The Archer) November 23 to December 21.
Capricorn (The Sea-goat) December 22 to January 20.
Aquarius (The Water Bearer) January 21 to February 18.
Pisces (The Fish) February 19 to March 20.
Zodiac sign for an individual depends on the placement of planets and the ascendant in that sign. If a person has nothing placed in a particular sign, that sign will play no active role in their personality. On the other hand a person with, for example, both the sun and moon in Cancer, will strongly display the characteristics of that sign in their make up.
Definition courtesy Wikipedia.