(2) "It has a double layer of semantics, its structure is fixed, the syntactic function is similar to the idiom, with rhetoric of demotic colloquialism 。"
(3) "As long as it has a fixed structure, without a double layer of meaning, and its implication is embodied in the general concept of a class rather than the concept of a particular thing or a specialized concept, it is a locution。"
《红楼梦》杨译本和霍译本的熟语翻译策略研究(3):http://www.youerw.com/yingyu/lunwen_161419.html