When saying goodbye, people in China often say "Bye Bye." But until this July there was no Chinese way of writing that. There is now: Beijing's guardians of the language have deemed "Bai Bai" the correct written form, and it has been included in the new edition of China's best-known dictionary. Actually the linguists took the matter a step further. There are four tones in spoken Mandarin, and the character "Bai" is spoken in the fourth, which has a very hard ring to it. To soften that, the linguists came up with a tailor-made, second tone "Bai.