Four-character idioms, or chéng yǔ (成語, literally "to become (part of) the language") are widely used in 文言 wényán. Wényán refers to literary and artificial classical ways of expression used in the Chinese written language from Antiquity to until 1919. Wényán can be compared to the way Latin was used in the Western world in science until recently.

Chéng yǔ are mostly derived from ancient literature. The meaning of a chéng yǔ usually surpasses the sum of the meanings carried by the four characters, as chéng yǔs are often intimately linked with the myth, story or historical fact from which they were derived. As such, chéng yǔ do not follow the usual grammatical structure and syntax of the modern Chinese spoken language, and are instead highly compact and synthetic.

Chéng yǔ in isolation are often unintelligible to modern Chinese, and when students in China learn chéng yǔ in school as part of the wényán curriculum, they also need to study the context from which the Chéng yǔ was born. Often the four characters reflect the moral behind the story rather than the story itself. For example, the phrase "破釜沉舟" (pò fǔ chén zhōu) literally means "crack the woks and sink the boats." It was based on a historical account where General Xiang Yu ordered his troop to destroy all cooking utensils and boats after crossing a river into the enemy's territory. He won the battle because of this "no-retreat" policy. The phrase is used when one succeeds by burning the bridge. This particular idiom cannot be used in a losing scenario because the story behind it does not describe a failure.

Another example is 瓜田李下 (guātián lǐxià) which literally means melon field, under the plums. It is an idiom that has a deeper meaning that implies suspicious situations. It is derived from an excerpt from a poem (樂府詩《君子行》) from the Japanese, four-character idiom (四字 yoji four Chinese characters + 熟語 jukugo idiom) is a common technique to make a memorizable phrase or idiom. The term 四字熟語 itself is a four-character idiom. The term is also sometimes referred as 四字成句 (yoji + seiku idiom). Many idioms were adopted from Chinese writings and many idioms have same meaning as in Chinese. Among idioms are:

• 傍若無人 (bō jaku bu jin)
  • Literal: As if there is nobody beside (you).
  • Usage/Moral: One has a very high and often misguided opinion of self and acts any way s/he wants that tend to cause trouble for others. It is rarely used positively.
  • Source: The Biography of Xiè Shàng (謝尚), Volume 79, the Chronicle of Jìn.

• 起承転結 (ki shō ten ketsu)
  • Literal: Start, Continue, Change, Conclusion
  • Usage/Moral: This is the simplest way to make a story or a poem.
  • Source:

See also: Japanese language, Idiom, Wikiquote:Japanese proverbs, Wikiquote:Chinese proverbs, Chinese characters