Collocation means the co-occurrence of words placed next to each other. It is defined as the arrangement or juxtaposition of words that commonly occur together. Simply speaking, it is merely the grouping of words. When two words are used together as a common practice, rules are formed about their use, not because of any grammatical reasons but due to their association.
For example, we always say 'black and white', and seldom hear anyone saying 'white and black'. The reverse order seems incorrect, not because there is any grammatical flaw, but just because one is used to reverse form of association. Similarly, we say a high mountain-peak or a tall man, but don't usually say a high man and a tall mountain-peak, only because it sounds odd to the ear.
For example, we always say 'black and white', and seldom hear anyone saying 'white and black'. The reverse order seems incorrect, not because there is any grammatical flaw, but just because one is used to reverse form of association. Similarly, we say a high mountain-peak or a tall man, but don't usually say a high man and a tall mountain-peak, only because it sounds odd to the ear.
