Both the Greek and the Chinese zodiac are astrological systems consisting of 12 symbols. In the Greek zodiac, four of the symbols are represented by human figures, while the rest are animals. In the Chinese zodiac, all 12 symbols are animals.

Each symbol, in both systems, represents a set of traits such as vanity, honesty, generosity and mischievousness. In the Greek zodiac, the symbols change from month to month. In the Chinese system, the symbols change each year. Many people believe that human personalities are determined by the sign under which they were born.

Constellations
The word zodiac means "circle of animals" in Greek. According to the website Zodiac Constellations, each year the sun moves eastward in an ellipse around the sky. As the sun moves during the day, 12 constellations around the edge of the ellipse take turns holding position directly overhead at night. Each constellation stays overhead for about 30 days. For the Greeks, marking the positions of these constellations was likely one way to mark the passing of the year.

Greek Zodiac Symbols
According to the Zodiac Constellations, all of the Greek zodiac symbols are taken from Greek myths. For instance, Aires was a ram with golden fur that could fly. Pieces, represented by two fish, comes from the legend of Aphrodite and Eros--the Greek gods of love--escaping a violent encounter by turning into two fish and swimming away. In each of these tales, Zeus turns important figures from the stories into constellations to honor them.

Greek Zodiac Personality Traits
Apart from simply being a way to keep track of the year, the zodiac is also believed to determine personality traits. For instance, according to Zodiac Signs Astrology.com, someone born from Oct. 24 to Nov. 22 is born under the sign of Scorpio. People born under this sign are said to be passionate, creative and manipulative. People born under Sagittarius, from Nov. 22 to Dec. 21, are said to be independent and supportive, yet unemotional.

Some people use these symbols to determine which people are most compatible together as friends and romantic partners.

Chinese Zodiac Symbols
The Chinese zodiac consists of 12 animals that change yearly instead of monthly. The order of the animals begins with the rat and continues: ox, tiger, rabbit, dragon, snake, horse, ram, monkey, chicken, dog and pig.

In Chinese mythology, the jade emperor (or sometimes Buddha) invites all the animals of the universe to a race ending in a banquet. The first 12 animals would be awarded with places in the zodiac, the order being determined by the order of the animals' arrival. All of the animals have adventures along the way, either attempting to cheat their way to the front, or falling behind because they stop to help others in need.

Chinese Zodiac Personality Traits
Like the Greek zodiac, many believe that a person's birth year according to the Chinese zodiac determines how that person behaves. For instance, those born in the Year of the Pig (begin in 1923 and add 12 for each subsequent year) are said to be loyal and intelligent, according to Wisegeek.com. Those born in the Year of the Dragon (beginning in 1928) are said to be blessed with good luck and charisma.

Different signs of the Chinese zodiac get along and conflict according to their inherent traits. Just as in the Greek zodiac, some people use the Chinese zodiac to determine with whom they are most compatible.