AbstractIdioms – or something like idioms – occupy a special place as a speech genre in languages. It is compelling that the issues of what idioms are (or are not) and how they distinguish themselves from other related, though different, linguistic and phraseological categories, are of concern to all. This paper first examines various linguistic issues concerning the idiom genre before going into a detailed discussion about the chengyu in Chinese, which is an approximate yet by no means identical counterpart of the idiom as it is understood in English. It is argued that, as phrasal structures, Chinese chengyus are not all lexically fixed, neither are they all semantically non-compositional. By virtue of the example of the sememe zhong lit. ‘(bronze) bell’ and its incorporation into certain chengyus, it is demonstrated that the sememic constituents of a chengyu can be only not compositionally significant semantically speaking but also, they may well hold the key to the reason why the literal meaning of a chengyu should be closely integrated into its intended, idiomatic (figurative) meaning. Chengyus that incorporate the sememe zhong comprise an idiomatic analogy and, in fact, zhong as a lexical item is represented in the content of this analogy as a cognitively real element. This paper adopts the Natural Semantic Metalanguage (NSM) framework as the basis for semantic analyses of such chengyus.