In Chinese zodiac compatibility tradition, the Dog forms a harmony group with the Tiger and Horse.
These three signs make up one of the four traditional “Three Harmonies” or trines. The group is commonly called the Tiger–Horse–Dog trine. Each trine contains three animals separated by four positions in the 12-sign cycle, and traditional interpreters regard members of a trine as naturally compatible or mutually supportive.
The system is distinct from the six direct-opposition pairings and from the four signs sometimes described as “secret friends.” Compatibility tables can differ in wording and in the personality traits assigned to each animal, but the Tiger, Horse, and Dog grouping is a standard feature of Chinese zodiac tradition.
These associations are cultural and astrological beliefs. They are not scientific measures of relationship quality, and traditional sources do not all agree on every detail of how compatibility should be interpreted.