These common groupings arrange the twelve year animals into four trines and six fixed harmony pairs.
Check any two signs against these groupings
The groupings above combine two different traditional ideas, which is worth separating because they are often blurred together.
The four trines (三合, sān hé) group animals that sit four places apart on the twelve-position cycle, forming a triangle: Rat, Dragon and Monkey; Ox, Snake and Rooster; Tiger, Horse and Dog; Rabbit, Goat and Pig. Tradition reads each trine as a set of temperaments that push in the same direction — the members are said to want similar things, so they are held to cooperate with little friction.
The six harmonies (六合, liù hé) are fixed pairs instead: Rat and Ox, Tiger and Pig, Rabbit and Dog, Dragon and Rooster, Snake and Monkey, Horse and Goat. This is the “secret friend” pairing, read as complement rather than similarity — each animal is said to supply what the other lacks. Every animal therefore has one secret friend and two trine partners, which is why three names appear beside each entry above.
Both are symbolic groupings within the cycle. A pair with no traditional link simply sits outside these named patterns; a shared trine supplies a useful language for comparing pace, priorities, and ways of cooperating.