What is a collocation?

A collocation is a combination of words that native speakers habitually use together. We say “heavy rain”, not “strong rain”; “make a decision”, not “do a decision”. They aren't governed by a rule — you learn them by exposure — and getting them right is one of the clearest signs of advanced, natural English.

Building collocations (verb + noun, adjective + noun) is often more useful than learning single rare words, because they make your writing sound fluent rather than translated.