The zodiac is the portion of the
celestial sphere that lies within 8¡ on either side of the ecliptic. The apparent
paths of the Sun, the Moon, and the principal planets, with the exception of some portions of the path of Pluto, lie within this band of the
celestial sphere.Twelve divisions, or signs, each 30¡ in width, comprise the zodiac. These signs coincided with the zodiacal
constellations about 2,000 years ago. Because of the precession of the Earth's axis, the vernal equinox has moved westward by about 30¡ since that time. The signs have moved with it and thus no longer coincide with the constellations. The signs are considered to be of great importance by astrologers (see astrology).