ABSTRACT
This chapter provides an overview of some multi-word expressions, most of them functioning as single units—either syntactically or semantically—that represent a challenge for the traditional limits between morphology, syntax and the lexicon. Morphologically, the second of the two verbs, known as the auxiliated verb, is a non-finite form, while the first, or auxiliary verb, is inflected varying in person, number, tense and mood. From a semantic viewpoint, the auxiliary verb is desemantised and has only grammatical content. Instead, the auxiliated verb carries the lexical meaning of the periphrasis. Regarding compositionality, a multi-word expression is said to be compositional if the meaning of the whole expression originates from the sum of meanings of its constituents; it is therefore a regular sum of the signifieds, signifiers and syntactics of its components. Semantically, idioms can be classified regarding the degree of its transparency/opacity into three subclasses.
