Agnes Mary Clerke,
1911 Encyclopædia Britannica, Volume 28…
(1911)
“ ZODIAC (ὁ ζωδιακὸς κύκλος, from ζώδιον, “a little animal”) , in astronomy and astrology, an imaginary zone of the heavens within which lie the paths of the sun, moon and principal planets. It is bounded by two circles equidistant from the ecliptic, about eighteen degrees apart; and it is divided into twelve signs, and marked by twelve constellations. ”
