noun

• (uncountable) The grouping or juxtaposition of things, especially words or sounds.
  "Everything in fact depends in Chinese on the proper collocation of words in a sentence. Thus ngò tà ni means “I beat thee;” but ni tà ngò would mean “Thou beatest me.”"
• (countable) Such a specific grouping.
  "We said at first breāk fâst—“I broke fast at such an hour this morning:” he, or they, who first ventured to say I breakfasted were guilty of as heinous a violation of grammatical rule as he would be who should now declare I takedinnered, instead of I took dinner; but good usage came over to their side and ratified the blunder, because the community were minded to give a specific name to their earliest meal and to the act of partaking of it, and therefore converted the collocation breākfâst into the real compound brĕakfast."
• (linguistics, translation studies) A sequence of words or terms that co-occur more often than would be expected by chance (i.e., the statistically significant placement of particular words in a language), often representing an established name for, or idiomatic way of conveying, a particular semantic concept.
  "Little and few are also incomplete negatives; note the frequent collocation with no: there is little or no danger."
• (mathematics) A method of finding an approximate solution of an ordinary differential equation L[y]=0 by determining coefficients in an expansion y(x)=y_0(x)+∑ₗ₌₀^qαₗy_l(x) so as to make L[y] vanish at prescribed points; the expansion with the coefficients thus found is the sought approximation.