Phraseme
A phraseme, also called a set phrase, fixed expression, idiomatic phrase, multiword expression (in computational linguistics), or idiom, is a multi-word or multi-morphemic utterance whose components include at least one that is selectionally constrained or restricted by linguistic convention such that it is not freely chosen. In the most extreme cases, there are expressions such as X kicks the bucket ≈ ‘person X dies of natural causes, the speaker being flippant about X’s demise’ where the unit is selected as a whole to express a meaning that bears little or no relation to the meanings of its parts. All of the words in this expression are chosen restrictedly, as part of a chunk. At the other extreme, there are collocations such as stark naked, hearty laugh, or infinite patience where one of the words is chosen freely (naked, laugh, and patience, respectively) based on the meaning the speaker wishes to express while the choice of the other (intensifying) word (stark, hearty, infinite) is constrained by the conventions of the English language (hence, *hearty naked, *infinite laugh, *stark patience). Both kinds of expression are phrasemes, and can be contrasted with ’’free phrases’’, expressions where all of the members (barring grammatical elements whose choice is forced by the morphosyntax of the language) are chosen freely, based exclusively on their meaning and the message that the speaker wishes to communicate.