Clash is an intense interaction between Earthly Branches, referring to two branches positioned in opposite directions that confront each other. The Six Clashes are: Zi (Rat) vs. Wu (Horse), Chou (Ox) vs. Wei (Goat), Yin (Tiger) vs. Shen (Monkey), Mao (Rabbit) vs. You (Rooster), Chen (Dragon) vs. Xu (Dog), and Si (Snake) vs. Hai (Pig). Clash signifies change, conflict, and separation; when a clash occurs, movement arises—stillness precludes clash. However, clashes may also be categorized as 'opening up' or 'dispersing', and thus must not be interpreted uniformly.
Examine the Earthly Branches in the four pillars of the八字 (BaZi) chart to identify whether any of the Six Clashes exist: Zi (Rat) vs. Wu (Horse), Chou (Ox) vs. Wei (Goat), Yin (Tiger) vs. Shen (Monkey), Mao (Rabbit) vs. You (Rooster), Chen (Dragon) vs. Xu (Dog), and Si (Snake) vs. Hai (Pig). A clash occurs whenever two opposing branches appear. Clash strength is strongest when the clashing branches occupy adjacent pillars; strength diminishes if separated by one or more branches.
In a BaZi chart, if the Year Branch is Zi (Rat) and the Day Branch is Wu (Horse), the Zi-Wu Clash manifests, indicating significant life changes occurring between youth and middle age.