A cleft sentence is a type of sentence structure that emphasizes a particular part of the sentence by splitting it into two clauses. This construction often uses the phrase "It is" or "It was" to highlight the subject or object, making the sentence clearer and more impactful. For example, instead of saying, "John won the race," a cleft sentence would be, "It was John who won the race." Cleft sentences are useful in both spoken and written language, as they help to draw attention to specific information. They can enhance clarity and focus, making them a valuable tool in communication. This structure is commonly used in English and can be adapted to various contexts, such as in literature or everyday conversation.