Collocations, i.e. arbitrarily restricted lexeme combinations such as make a decision or fully aware, are one type of a group of expressions whose importance in language has been increasingly recognized in recent years.

This group of expressions has been variously called prefabricated units, prefabs, phraseological units, (lexical) chunks, multi-word units, or formulaic sequences.1 They are made up of more than one word and are lexically and/or syntactically fixed to a certain degree.

Following a period in which, largely due to the wide influence of generative grammar, prefabricated units were considered peripheral in language, it is today widely assumed that their number is vast and that they play a major role in language processing and use.