哈哈 is an onomatopoeic interjection for laughter, used in spoken and written Chinese to show amusement, joy, or sometimes mild sarcasm. It mirrors the natural sound of laughter and often appears at the beginning of a sentence or as a standalone utterance. Unlike English "ha-ha", which can be used with a period in writing, Chinese 哈哈 is commonly written with two characters and can be extended (哈哈哈哈) for emphasis.