Yojijukugo

Yojijukugo (^?) is a Japanese lexeme consisting of four kanji (Chinese characters). English translations of yojijukugo include "four-character compound", "four-character idiom", "four-character idiomatic phrase", and "four-character idiomatic compound". It is equivalent to the Chinese chengyu.

The definition of yojijukugo is somewhat murky since the Japanese word jukugo (^?, literally "ripe/mature/popular word") can linguistically mean "compound", "idiom", or "phrase".

Yojijukugo in the broad sense simply means any Japanese compound words consisting of four kanji characters. In the narrow or strict sense, however, the term refers only to four-kanji compounds that have a particular (idiomatic) meaning that cannot be inferred from the meanings of the components that make them up.

There exists a very large number — perhaps tens of thousands — of four-character compounds. A great majority of them are those whose meanings can be easily deduced from the literal definition of their parts. These compounds may be called non-idiomatic yojijukugo.

For example, the compound word 屋内禁煙 okunaikin'en "no smoking indoors" is a non-idiomatic yojijukugo. It is made up of four characters: 屋 oku building, 内 nai inside, 禁 kin prohibited, and 煙 en smoking. Alternatively, it can be regarded as consisting of two common two-character compounds: 屋内 okunai indoors, and 禁煙 kin'en prohibition of smoking. Either way, the meaning of the compound is clear; there are no idiomatic meanings beyond the literal meanings of its components. Below are a few more examples of non-idiomatic yojijukugo:

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