Four-character idioms are widely used in Chinese language as cheng yu (成語 pinyin chéng yǔ, literally "to become (part of) the language"). Cheng yu are mostly quotes from ancient literature. Many of these idioms carry meanings much more than the sum of the four characters. When students in China learn cheng yu in school, they need to study the stories behind the phrases. Often the four characters are just a hint to the moral behind those stories. For example, the phrase (破釜沉舟) literally means crack the woks and sink the boats. It was based on a historical account where a general 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 is never used in a losing scenario because the story behind it does not describe a failure.
The following three examples show that the meaning of the idiom can be totally different by only changing one character.
In Japanese language, four-character idiom (四字 Shiji or Yoji four Chinese characters + 熟語 Jyukugo 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). Among idioms are: