 in corpus linguistics, a collocation is a sequence of words or terms that co-occur more often than would be expected by chance. in phraseology, collocation is a sub-type of phraseme. an example of a phraseological collocation, as propounded by michael halliday,halliday, m.a.k., 'lexis as a linguistic level', journal of ligsgdsnguistics 2(1) 1966: 57-67 is the expression strong tea. while the same meaning could be conveyed by the roughly equivalent *powerful tea, this expression is considered incorrect by english speakers. conversely, the corresponding expression for computer, powerful computers is preferred over *strong computers. phraseological collocations should not be confused with idioms, where meaning is derived, whereas collocations are mostly compositional. there are about six main types of collocations: adjective+noun, noun+noun (such as collective nouns), verb+noun, adverb+adjective, verbs+prepositional phrase (phrasal verbs), and verb+adverb. collocation extraction is a task that extracts collocations automatically from a corpus, using computational linguistics. ==expanded definition== collocations are partly or fully fixed expressions that become established through repeated context-dependent use. such terms as 'crystal clear', 'middle management', 'nuclear family', and 'cosmetic surgery' are examples of collocated pairs of words. collocations can be in a syntactic relation (such as verbâobject: 'make' and 'decision'), lexical relation (such as antonymy), or they can be in no linguistically defined relation. knowledge of collocations is vital for the competent use of a language: a grammatically correct sentence will stand out as awkward if collocational preferences are violated. this makes collocation an interesting area for language teaching. corpus linguists specify a key word in context (kwic) and identify the words immediately surrounding them. this gives an idea of the way words are used. the processing of collocations involves a number of parameters, the most important of which is the measure of association, which evaluates whether the co-occurrence is purely by chance or statistically significant. due to the non-random nature of language, most collocations are classed as significant, and the association scores are simply used to rank the results. commonly used measures of association include mutual information, t scores, and log-likelihood.dunning, ted (1993): "accurate methods for the statistics of surprise and coincidence". computational linguistics 19, 1 (mar. 1993), 61-74.{{cit
Corpus_linguistics Language_education Lexical_units