Description:On the basis of a corpus of 273 cases, the study examines phraseological pair formations in standard present-day French, such as de fil en aiguille or au fur et à mesure, for the features that constitute and structure them. The heart of the study is a classification of idiomatic meaning formation according to types. Characteristic phonological and morphological aspects are discussed, and the study also indicates formal and semantic principles that prove to be co-determinant for the order of the components in two-part idiomatic expressions.