Stick Suit
The stick suit was originally represented by spears, but is shown as bamboo in most modern sets. This suit, numbered from one to nine, signifies the axis of the earth.
Wheel Suit
Called "tung" in Chinese and meaning wheels, this suit is represented by circles or dots in mahjong sets. The dots represent the wheels of heaven.
Number Suit
The numbers are called "shu" in Chinese and symbolize the changes humans go through during their lifetime.
Seasons, Wind, and Flowers
When the tiles form a square, it characterizes the universe. The heavens reveal themselves in the four seasons (spring, summer, autumn and winter) and the earth is divided into the four regions (north, south, east and west winds). The four flowers symbolize man and the motions of life.
Dragons
There are three different dragons in mahjong (red, white and green). The red dragon symbolizes man and the center between heaven and earth. The white dragon indicates heaven, while the green dragon denotes earth.