Collocations are sequences of words that occur with one another. These sequences can be viewed as fixed expressions. Collocations can be classified as strong and weak. Strong collocations are collocations in which the link between two words is restricted. On the other hand, weak collocations have a word which can combine with many other words.
The words fast and quick have similar meanings, but speakers say fast food and quick meal. In the case of big and great, they say big surprise and great fun. When the topic is size, speakers say small, medium and large. Here the word big is incorrect. Both high building and tall building sound fine, but speakers use high temperature and tall man.
Few words can precede wish. It's possible to say grant a wish, make a wish and express a wish. Since few words can combine with wish, the ones that do form strong collocations. Another example is winding. This word is often used in the phrase winding road. It doesn't combine with many words and is thus another example of a strong collocation.
However, the word big can combine with many words. A few include big house, big disappointment and big idea. For this reason, it's classified as a weak collocation. Another example is strong: strong coffee, strong boy and strong character.
Words which combine naturally are collocations. Though words can often be used interchangeably, i.e., run fast, run quickly, this is not so for collocations. They are word sequences whose order is fixed.