哈哈
hāhā · HSK 3
haha
😂 哈 + 哈 = ha + ha; reduplicated onomatopoeia for laughter
哈 (hā) mimics an open-mouthed exhale, the same sound English writes as ha. Doubling it to 哈哈 is Mandarin's standard way to spell out laughter in text, just like English haha or LOL.