One word for this phenomenon is collocation - which is defined in many ways, but generally refers to two or more words which have a tendency to co-occur. The wikipedia page (https://en.wikipedia.org/wiki/Collocation) currently defines it both as 'a sequence of words or terms that co-occur more often than would be expected by chance' and as 'partly or fully fixed expressions that become established through repeated context-dependent use' (two different definitions with different theoretical implications). Examples on the Wikipedia page include 'nuclear family' and 'make a decision'.
Research is ongoing to explore the idea that collocations are (mentally) processed differently from other groupings of words. A good starting-point to read about this could be Michael Hoey's theory of lexical priming, which holds that what we know about a word comes from our experience of it, so that our mental representation of it includes knowledge about the words it tends to co-occur with. Hence when we encounter word X, we will more easily retrieve words which often co-occur with word X than words which co-occur less often with word X. An example of a study referring to lexical priming in relation to language processing is Gagné (2001) .
 Gagné, C. L., (2001), 'Relation and lexical priming during the interpretation of noun–noun combinations.', Journal of Experimental Psychology: Learning, Memory, and Cognition, Vol 27(1), Jan 2001, 236-254. See: http://psycnet.apa.org/journals/xlm/27/1/236/