What can a corpus tell us about multi-word units?

This chapter describes how corpus linguistics can enable researchers, teachers and learners to better understand and explore multi-word units. One of the most important findings from the field of corpus linguistics has been the full extent of what Sinclair termed the idiom principle, by which he meant the phraseological nature of language through the co-selection of words by speakers and writers. The co-selection of words has been studied prior to the arrival of electronic corpora, but the prevalence of these co-selections and their forms and functions have now been fully established thanks to the tools available to the corpus linguist. This chapter begins by explaining the importance of a better understanding of the role of multi-word units and then proceeds to describe the main forms of the multi-word units and their functions. The chapter concludes with an overview of the more recent studies of phraseological variation which seek to expand our understanding by moving beyond fixed contiguous co-selections to include multi-word units which exhibit variation, whether that be constituent, positional or both.