Origin of the Chinese Zodiac
The pairing of the Twelve Zodiac Animals with
the Twelve Earthly Branches follows the corresponding rules of yin–yang attributes.
Rat
Zi (子) is yang.
The Zi hour sits at the boundary between yin and yang. Although the hour as a whole belongs to yang, when it is divided into eight quarters, the first four quarters carry over from the previous night and belong to yin, while the last four quarters open the new day and belong to yang. This yin–yang crossing corresponds exactly to the rat's physical structure: the rat's forefeet have four toes (an even number = yin), while its hind feet have five (an odd number = yang), perfectly matching the yin–yang boundary of the Zi hour.
Ox
Chou (丑) is yin
the ox's hoof is cloven into two (even = yin).
Tiger
Yin (寅) is yang
the tiger has five claws (odd = yang).
Rabbit
Mao (卯) is yin
the rabbit has a cleft lip and four claws (even = yin).
Dragon
Chen (辰) is yang
the dragon has five claws (odd = yang).
Snake
Si (巳) is yin
the snake's forked tongue splits in two (even = yin).
Horse
Wu (午) is yang
the horse's hoof is round and undivided, a single whole (odd = yang).
Goat
Wei (未) is yin
the goat's hoof is cloven into two (even = yin).
Monkey
Shen (申) is yang
the monkey has five claws (odd = yang).
Rooster
You (酉) is yin
the rooster has four claws (even = yin).
Dog
Xu (戌) is yang
the dog has five claws (odd = yang).
Pig
Hai (亥) is yin
the pig's hoof is cloven into two (even = yin).