Begun is the past participle of the verb “begin,” which means to start or commence something. You use it after helping verbs like “has,” “have,” or “had.” For instance, you might say “The concert has begun” or “By the time we arrived, the movie had already begun.”

The tricky part is knowing when to use begun versus began. Use began when talking about something that started in the past: “The game began at noon.” Use begun when you need a helping verb: “The game has begun.”

Think of it this way: if you can put “has,” “have,” or “had” before the word, you need begun. If you're stating simply that something started at a specific time in the past, you need began. Many people mix these up, saying things like “The show has began” (incorrect) or “The show begun at eight o'clock” (also incorrect).

You'll see begun in formal announcements or dramatic moments: “The journey has begun,” or “Once you've begun reading that book, you won't want to put it down.” There's something about the word that suggests a significant start, the first step of something that will continue or grow.