Common collocations are pairs or groups of words that are frequently used together in a language. These word combinations have become so common that they are often considered as a single unit of meaning. Collocations can be formed by adjectives and nouns, verbs and adverbs, or prepositions and nouns. Examples of common collocations include "heavy rain," "fast food," "make a decision," "take a shower," and "in the morning." Understanding and using collocations correctly can help improve your fluency and accuracy in a language.