A clause is a group of words that contains a subject and a verb. It can express a complete thought, making it an independent clause, or it can be part of a larger sentence, known as a dependent clause. For example, in the sentence "She runs fast because she practices," "She runs fast" is an independent clause, while "because she practices" is a dependent clause. Clauses are essential in constructing sentences and can be combined to add complexity and detail. They can be categorized into different types, such as noun clauses, adjective clauses, and adverb clauses, each serving a unique function in a sentence. Understanding clauses helps improve writing clarity and coherence.