They are often referred to as Chinese idioms or four-character idioms; however, they are not the only idioms in Chinese.
Chengyu are mostly derived from ancient literature. The meaning of a chengyu usually surpasses the sum of the meanings carried by the four characters, as chengyu are often intimately linked with the myth, story or historical fact from which they were derived. As such, chengyu do not follow the usual grammatical structure and syntax of the modern Chinese sopken language, and are instead highly compact and synthetic.
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