zodiac [Gr. zoion=animal], in astronomy, zone of the sky that includes about 8° on either side of the ecliptic. The apparent paths of the sun, the moon, and the major planets all fall within this zone. The zodiac is divided into 12 equal parts of 30° each, each part being named for a constellation, each of which is represented by a sign and many of which have animal names. The constellations and their corresponding symbols and dates are listed in the table entitled The Signs of the Zodiac. The zodiac serves as a convenient means of indicating the positions of the heavenly bodies. When the constellations of the zodiac were named about 2,000 years ago, the vernal equinox coincided with the beginning of the constellation Aries. For this reason, the first 30° section of the zodiac is called Aries; it extends eastward 30° from the vernal equinox, which is therefore called the first point of Aries. However, because of the precession of the equinoxes, the vernal equinox has moved westward about 30° and now lies in the constellation Pisces; the zodiacal constellations thus no longer correspond to the segments of the zodiac represented by their signs. The constellations will again coincide with the sections of the zodiac in about 25,800 years. The zodiac probably had its origins among the Assyrians or Chaldaeans, although it may have originated among the Babylonians as early as 2000 B.C. It is of importance in astrology.

Constellation	English Name	Symbol	Dates
Aries	The Ram	♈	Mar. 21-Apr. 19
Taurus	The Bull	♉	Apr. 20-May 20
Gemini	The Twins	♊	May 21-June 21
Cancer	The Crab	♋	June 22-July 22
Leo	The Lion	♌	July 23-Aug. 22
Virgo	The Virgin	♍	Aug. 23-Sept. 22
Libra	The Balance	♎	Sept. 23-Oct. 23
Scorpio	The Scorpion	♏	Oct. 24-Nov. 21
Sagittarius	The Archer	♐	Nov. 22-Dec. 21
Capricorn	The Goat	♑	Dec. 22-Jan. 19
Aquarius	The Water Bearer	♒	Jan. 20-Feb. 18
Pisces	The Fishes	♓	Feb. 19-Mar. 20

Belt around the heavens extending about 9° on either side of the ecliptic. The orbits of the Moon and the major planets lie entirely within the zodiac. In astrology, each of 12 constellations along this circle is considered to occupy 1/12 (30°) of it. The positions of the Sun and planets when a person is born and their motion through these constellations are said to exert influence on his or her life, though precession of the equinoxes has shifted the constellations eastward, and the Sun no longer passes through them on the traditional dates: Aries, the ram (March 21–April 19); Taurus, the bull (April 20–May 20); Gemini, the twins (May 21–June 21); Cancer, the crab (June 22–July 22); Leo, the lion (July 23–August 22); Virgo, the virgin (August 23–September 22); Libra, the balance (September 23–October 23); Scorpius (see Scorpio), the scorpion (October 24–November 21); Sagittarius, the archer (November 22–December 21); Capricornus (see Capricorn), the goat (December 22–January 19); Aquarius, the water bearer (January 20–February 18); Pisces, the fish (February 19–March 20).

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