MEANING: noun:
1. A circular diagram with 12 parts, each named after a constellation, used in astrology.
2. A circle, circuit, etc.

ETYMOLOGY: From Latin zodiacus, from Greek zoidiakos, shortening of zoidiakos kyklos (zodiac circle), from zoion (living being) + kyklos (circle, wheel). Earliest documented use: 1390.

KODIAC - an Alaskan ursine, sometimes barely visible

AZODIAC - a nitrogen-containing compound with two acetate radicals

OZODIAC - a supermolecule combining two molecules of ozone - used to assist in replenishing the hole in the atmosphere