|Wu Chinese (Shanghainese)||sy2||sy2,shi2|
|Min Nan (Taiwanese Hokkien)||sì,sù||sí,sú|
Tetraphobia (from Greek τετράς - tetras, "four" and φόβος - phobos, "fear") is the practice of avoiding instances of the number 4. It is a superstition most common in East Asian and Southeast Asian regions such as China, Taiwan, Singapore, Malaysia, Japan, Korea and Vietnam.
The Chinese word for four (四, pinyin: sì, jyutping: sei3), sounds quite similar to the word for death (死, pinyin: sǐ, jyutping: sei2), in many varieties of Chinese. Similarly, the Sino-Japanese, Sino-Korean, and Sino-Vietnamese words for four, shi (Japanese), sa (사, Korean) and tư (Vietnamese), sound similar or identical to death in each language (see Korean numerals, Japanese numerals, Vietnamese numerals).
Special care may be taken to avoid occurrences or reminders of the number 4 during festive holidays, or when a family member is sick. Similarly, 14, 24, 42, etc. are also to be avoided due to the presence of the digit 4 in these numbers. In these countries, these floor numbers are often skipped in buildings, ranging from hotels to offices to apartments, as well as hospitals. Table number 4, 14, 24, 42, etc. are also often left out in wedding dinners or other social gatherings in these countries. In many residential complexes, building block 4, 14, 24 etc. are either omitted or replaced with block 3A, 13A, and 23A.
The Chinese government does not display tetraphobia by having military designations for People's Liberation Army with the number 4, for example, Dongfeng-4 ICBM, Type 094 Nuclear Submarine, Type 054A Frigate, etc. But the Taiwanese and the South Korean navies do not use the number 4 when assigning Pennant numbers to their ships.
In Hong Kong, some apartments such as Vision City and The Arch skipped all the floors from 40 to 49. Immediately above 39/F is 50/F, leading many who are not aware of tetraphobia to believe that some floors are missing. Tetraphobia is not the main reason, but rather as an excuse to have apartments with 'higher' floors, thus increasing price, because higher floors in Hong Kong apartments are usually more expensive. In Cantonese-speaking regions in China, 14 and 24 are considered more unlucky than the individual 4, since 14 sounds like "will certainly die" (實死) and 24 like "easy to die" (易死).
In Korea, tetraphobia is less extreme, but the floor number 4 is almost always skipped in hospitals and similar public buildings. In other buildings, the fourth floor is sometimes labeled "F" (Four) instead of "4" in elevators. Apartment numbers containing multiple occurrences of the number 4 (such as 404) are likely to be avoided to an extent that the value of the property is adversely affected. The national railroad, Korail, left out the locomotive number 4444 when numbering a locomotive class from 4401 upwards.
In Japan, many apartment houses and parking lots skip 4. Many hotels skip the 13th floor, similar to some western hotels. 9 is also skipped in some contexts, especially hospitals, due to the sound "ku" being associated with the word "kurushimu", to suffer. 49 is considered to be an especially unlucky number as it is evocative of the phrase "shinu made kurushimu" (死ぬまで苦しむ, "to suffer until death").
The software platform Symbian, used by Finnish telecommunications firm Nokia in their Series 60 platform, avoids releases beginning with 4, as it did when it was EPOC and owned by Psion (there was no Psion Series 4, and there was no 4th edition of S60). This was done "as a polite gesture to Asian customers".[dead link] However some of Nokia's non-Symbian products do contain the number 4, such as the Series 40 platform.
When area code 306 was nearing exhaustion in 2011, the Canadian Radio-television and Telecommunications Commission originally proposed that the new area code be 474 . However, representatives from SaskTel requested that the new area code be 639 instead, to avoid the negative connotations of 4 in Asian cultures . 639 was subsequently approved as the new area code. 
|Wikimedia Commons has media related to: Tetraphobia|
- Numbers in Chinese culture
- Thirteenth floor
- Triskaidekaphobia (the fear of the number 13)
- Curse of 39
- Faux pas derived from Chinese pronunciation
- τετράς, Henry George Liddell, Robert Scott, A Greek-English Lexicon, on Perseus
- φόβος, Henry George Liddell, Robert Scott, A Greek-English Lexicon, on Perseus
- Havil, Julian (2007). Nonplussed: Mathematical Proof of Implausible Ideas (Hardcover). Princeton University Press. p. 153. ISBN 0-691-12056-0.
- Floor plan remarks of Vision City
- Floor plan of The Arch