Multiword expressions (MWEs) are expressions which are made up of at least 2 words and which can be syntactically and/or semantically idiosyncratic in nature. Moreover, they act as a single unit at some level of linguistic analysis. According to Sag et al. we could define MWEs roughly as „idiosyncratic interpretations that cross word boundaries“. MWEs are communly used in any field of language – Jackendoff estimates the number of MWEs in a speaker's lexicon as comparable to the number of single words. Expamples for MWEs would be idioms as „kick the bucket“, compound nouns as „telephone box“ and „post office“, verb-particle constructions as „look sth. up“ or proper names as „San Francisco“. Due to the high frequency of MWEs there is a growing awareness in the NLP community for the problems they pose.
Timothy Baldwin et al.: An Empirical Model of Multiword Expression Decomposability (2003) in: Proceedings of the ACL 2003 Workshop on Multiword Expressions: Analysis, Acquisition and Treatment, pp. 89-96.
Nicoletta Calzolari et al.: Towards Best Practice for Multiword Expressions in Computational Lexicons (2002) in: Proceedings of the Third International Conference on Language Resources and Evaluation (LREC 2002), pp. 1934–40.
Ray Jackendoff: The Architecture of the Language Faculty (1997), Cambridge, MA: MIT Press.
Ivan A. Sag et al.: Multiword Expressions: A Pain in the Neck for NLP (2002) in: LECTURE NOTES IN COMPUTER SCIENCE, Vol. 2276, pp. 1-15.
Eric Wehrli: Parsing and Collocations (2000) in: LECTURE NOTES IN COMPUTER SCIENCE, Vol. 1835, pp. 272-282.