It’s a real pleasure to see a thorough and effective definition of a term that is frequently contested or confusing. Here’s Batia Laufer and Tina Waldman’s definition of collocation from their article “Verb-Noun Collocations in L2 Writing” from the June 2011 issue of Language Learning.
“We regard collocations as habitually occurring lexical combinations that are characterized by restricted co-occurrence of elements and relative transparency of meaning. Restricted co-occurrence distinguishes collocations from free combinations in which the individual words are easily replaceable following the rules of grammar. Relative semantic transparency of collocations, on the other hand, distinguishes them from idioms whose meaning is much less transparent than that of collocations and is very often opaque because it cannot be understood from the words that compose them. Some examples of restricted co-occurrence are the following: tea collocates with strong but not with powerful, discussion collocates with hold or have but not with deliver, and speech collocated with deliver but not with hold. Relative semantic transparency is illustrated by the following example: face in ’face a problem’ is not used with its original meaning, but the expression is clearer than ’face the music,’ an idiom that means ’show courage.’ Many collocations are totally transparent if the learner is familiar with the individual words (e.g., ’apply for a job,’ ‘make a decision,’ ‘submit a proposal’). Restricted co-occurrence and semantic transparency place collocations on the continuum between free combinations and idioms. Thus, according to the definition used in this article, we consider ’throw a disk’ and ’pay money’ to be free combinations, we consider ’throw a party’ and ’pay attention’ to be collocations, and we consider ’throw someone’s weight around’ and ’pay lip service’ to be idioms.”