Patterns the stars appear to form on the celestial sphere.  The modern definition of  a constellation is a specific area of the sky marked off with a boundary.  There are 88 official constellations.

Clusters of stars which have been grouped by the ancients in order to map the night sky for various purposes. 12 of these are the zodiac.

The groupings of fixed stars, (Orion, Big Dipper,Scorpio, etc.). Twelve of these groupings are named for the twelve sections that the Sun's path travels in one year as appeared from the Earth. It is these twelve sections that lend their name to the twelve signs of the Zodiac. In Astrology, it is not the constellations that are important it is the Sign of Zodiac.

Apparent arrangement of stars, usually named after ancient gods, heroes, animals or mythological beings.

A circle beyond the zodiac, bearing sections with the same names as the signs, containing defined groups of fixed stars, known as constellations. Ancient astrology had only forty-eight named constellations, although modern astronomers have named many more for convenience of location. There are no fixed stars in the zodiac; only planets inhabit the zodiac. Signs should not be confused with constellations, even though for historical reasons they may bear the same name. See also Lunar Mansions, which are based on Asterisms, or minor constellations.