First look carefully at the picture of the elevator control panel from our hotel -- something is wrong with it yet it is approximately the same as every elevator I've been in in Taiwan. Do you see it? Or, as I should say, do you not see it?
In Mandarin the word for four sounds like 'si' with a descending tone, while the word for death has the same phonetic pronunciation as 'si' but with the lower, descending then rising tone. The characters don't look anything alike:
四 = four
死 = death
In any case, because the words are homophones, only varying in tone, 'si' is the most dreaded number in Chinese culture. Your cashier will shudder if your change is 444. And, more importantly, no one would rent a room on the fourth floor, so hotels and apartment buildings do without them. When I first moved to Taiwan, I rented a room on a 'fifth' floor, which was really a fake fourth floor.
When you buy a Chinese set of teacups there will be five cups and never four in the set. Who wants to drink tea with the phantom of death lingering in the air!?
Other numbers are luckier however, especially 八 'ba' 8 which only has good connotations with lucky homophones. License plates, phone numbers, and security deposit boxes can often be auctioned off for thousands of dollars. The Beijing Olympics apparently started the opening ceremony at 8 seconds, 8 minutes after 8 o'clock on 8/8/08.