COLLOCATION.
1. The act of putting two or more things together, especially words in a pattern, and the result of that act.

2. In LINGUISTICS, a habitual association between particular words, such as to with fro in the phrase to and fro, and the uses of to after answer and before me in You'll answer to me (as opposed to You'll answer me). In the phrase Let's draw up a list, the phrasal verb draw up is said to collocate with the noun list; one can draw up a list of legal terms but not *draw up legal terms (although one can list legal terms). Collocation is basic to language. Its subtleties must be learned, and failure to get the collocations of English right is a major indicator of foreignness: for example, talking about rotten rather than rancid butter. IDIOMS are usually fixed in form and used without recourse to the meanings of their elements: it can rain cats and dogs, but never *dogs and cats or *cats and cows. Even with idioms, however, there can be some leeway: for example, at least the three verbs banging, hitting, and knocking can occupy the slot in the idiomatic sentence It's like—your head against a (brick) wall. Collocations are more loosely associated than idioms: contiguously (as with tortoise and shell in tortoiseshell) or proximately (as with cat and purr in The cat was purring). When the elements of compound words collocate, they form new lexical items: house and boat coming together in both houseboat and boathouse, each with a distinct meaning and use. An item that collocates with another is its collocate.

Collocation

a group or sequence formed by placing things side by side or in a place or position. e.g., words in a sentence or sound in music—Wilkes.

Examples: collocation of intervals and pores, 1684; of magazines, 1813; of poetry, 1873; of various metals, or inlaying them by way of ornament, 1881; of vowels and consonants, 1751; of words, 1750.