Off topic, but... Japanese and Chinese use the same system of characters for numbers. Also note that written Chinese is used by more than one Chinese language. The number four is considered unlucky in Japanese and at least Cantonese and Mandarin because the sound of the word is homophonous with the word for death. Such homophones are more common in Chinese languages vs Japanese because they are tonal, whereas Japanese is not. However,
the Japanese language and writing system has had strong influences from China, which is why they use the same characters for numbers and why there is some similarity in their words for these numbers.
If I had to guess, I would think mainland China would be less superstitious than Japan and that maybe this would account for the difference in avoidance of the number four.
Originally posted by boriscleto The 4th floor thing is mostly in Japan I believe. The Japanese character for the number 4 is the same as the character for death (Shi), therefore it is considered unlucky.