"Begun" is the past participle of the verb "begin," which means to start or commence something. It is often used in various contexts, such as initiating a project, event, or process. The term is commonly found in both spoken and written English, indicating that an action has already started. In grammar, "begun" is typically used with auxiliary verbs like "have" or "has" to form perfect tenses. For example, one might say, "I have begun my homework," which indicates that the action of starting the homework is complete, but the homework itself may still be ongoing.