Collocations refer to natural affiliations between closely related words. The relationship can be based on continuous usage over time or proven effectiveness. For example, we say "super-fast train" but not "super quick train". There are seven types of collocations formed by combining different parts of speech, such as adjective+noun, noun+verb, and verb+adverb combinations. Mastering collocations helps convey meaning precisely and effectively in both formal and informal communication.