Questions related to idioms, maxims, sayings, and other expressions consisting of a combination of words that has an indirect, figurative meaning. Use also the tag [chengyu] for questions about chengyu's.
In linguistics, idiomaticity is defined as the following:
Use of segmentally complex expressions whose semantic structure is not deducible jointly from their syntactic structure and the semantic structure of their components. -- Weinreich (1972:89)
In Chinese, the most popular kind of idiom is the chengyu 成语, (usually) four-character idioms.