fēn​jiǔ​bì​hé, hé​jiǔ​bì​fēn

constant change

分久必合,合久必分 fēn​jiǔ​bì​hé, hé​jiǔ​bì​fēn
constant change
The figurative notion that circumstances, relationships, or global trends are in a continuous state of flux and alternation.
unity and division
The literal historical cycle where entities long divided eventually unify, and those long unified eventually divide, as popularized by Romance of the Three Kingdoms.

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Definitions
CC-CEDICT