There are different ways to classify collocations, or words that are frequently used together. Collocations can be classified by their grammatical structure, such as adjective + preposition or noun + particular verb form. Another classification is lexical collocations, where a word like a verb, noun, adjective or adverb forms a predictable connection with another word. Examples are given of common collocations that frequently go together versus rare collocations not often seen. In general, collocations refer to words that are very closely associated with each other based on their frequent usage patterns.