|Wu Chinese (Shanghainese)||sy²||sy², shi²|
|Min Nan (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 Asian nations 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 (し, Japanese), and sa (사, Korean), 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 everyday life, especially during festive holidays, or when a family member is ill. Just mentioning the number 4 around a sick relative is strongly avoided. Giving four of something is strongly discouraged, and a popular idiom states that "you don’t do things in fours…". Elevators in Asia and Asian neighborhoods will often skip the 4th floor or any floor whose number contains the digit "4" (as 14, 24, etc.). Military aircraft and ships will also avoid the number 4 (such as the South Korean and Taiwanese navies) due to its extreme negative connotations of death. April 4 is also considered an exceptionally unlucky day (much like Friday the 13th in the West).
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. Hospitals are of grave concern and the number 4 is regularly avoided altogether. Tetraphobia can dictate property prices. Neighborhoods have removed four from their street names and become more profitable as a result. In the same way, buildings with multiple fours can suffer price cuts of up to $30,000-$50,000. Four is also avoided in phone numbers, security numbers, business cards, addresses, ID numbers, and other numbers and are considered severe as they are personally attached to the person. Giving such numbers to Asian persons is considered extremely offensive and even grounds for law enforcement involvement or legal retaliation due to it being easily seen as a death threat and has been used as such by gangs, organised crime groups, and murderers.
Chinese is a tonal language with a comparatively small inventory of permitted syllables, resulting in an exceptionally large number of homophone words. Many of the numbers are homophones or near-homophones of other words and have therefore acquired superstitious meanings.
The Chinese avoid phone numbers and addresses with fours, especially when they’re combined with another number that changes the meaning. Example: “94” could be interpreted as being dead for a long time.
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. However some speculate that it does for aircraft (just as the United States generally skips the number 13 for their aircraft), seeing that it begins aircraft and engine destination with 5. 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 skip all the floors from 40 to 49, which is the entire 40s. Immediately above the 39th floor is the 50th floor, 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 (see 39 Conduit Road). 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). While in Mandarin-speaking regions in China, 14 and 74 are considered more unlucky than the individual 4, since 14 sounds like "wants to die" (要死) and 74 like "will certainly die" or "will die in anger" (氣死).
Where East Asian and Western cultures blend, such as in Hong Kong, it is possible in some buildings that both the thirteenth floor and the fourteenth floor are skipped, causing the twelfth floor to precede the fifteenth floor, along with all the other 4s. Thus a building whose top floor is numbered 100 would in fact have just seventy-nine floors.
When Beijing lost its bid to stage the 2000 Olympic Games, it was speculated that the reason China did not pursue a bid for the following 2004 Games was due to the unpopularity of the number 4 in China. Instead, the city waited another four years, and would eventually host the 2008 Olympic Games, the number eight being a lucky number in Chinese culture.
In Taiwan not using house numbers ending in 4 without remembering to occasionally skip numbers on the opposite side too, often results in the two sides of a street getting more and more out of sync as one advances. 
In Southeast Asia
Because of the significant population of Chinese and influence of Chinese culture in Southeast Asia, 4 is also considered to be unlucky.
Singaporean public transport operator SBS Transit has omitted the number plates for some of its buses whose numbers end with '4' due to this, so if a bus is registered as SBS***3*, SBS***4* will be omitted and the next bus to be registered will be SBS***5*. Note that this only applies to certain buses and not others and that the final asterisk is a checksum letter and not a number.
In addition, Samudera LRT Station has been closed until 2020 as the code signifies the homonym of "death". The station between Hillview and Beauty World had the number skipped too, which is the Downtown MRT Line.
In Vietnam, the Sino-Vietnamese words for "four" (tứ) is used more in formal context than in everyday life and its spoken sound is clearly different from word for "death" (tử). The Chữ nôm word "bốn" equivalent to word "tứ" is often used, therefore the number 4 is rarely avoided. Even so, in the past Vietnamese people often named their children "tư" or "tứ", which means "the fourth child born in family".
In South Korea
In South 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 labelled "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 car parks skip 4. Many hotels skip the 13th floor, similar to some western hotels. There is also much wordplay involved such as 24 can become nishi, aka double death (ニ死), 42 can become shini, aka "death" or “to death” (死に), 43 can become shisan which sounds like shizan, aka stillbirth (死産), 45 can be shigo, or “after death” (死後). 9 is also skipped, especially hospitals, due to the sound "ku" being associated with the word "to suffer" (「苦しむ」 "kurushimu"?). 49 is considered to be an especially unlucky number as it is evocative of the phrase "To suffer until death." (「死ぬまで苦しむ。」 "Shinu made kurushimu."?)
Richmond Hill, Ontario, banned the number four on new houses in June 2013; property developers in Vancouver omitted the number from new buildings until October 2015, when the city banned non-sequential numbering schemes.
Examples of sensitivity to tetraphobia applied
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". Similarly, Nokia did not release any products under the 4xxx series, although some of Nokia's other products do contain the number 4, such as the Series 40 platform, and the Nokia 3410.
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.
Starting from Q4 2008, Samsung Telecommunications faced tetraphobia in its new 5-character model numbering scheme and no longer uses model codes containing the number 4, as previously it did (SGH-A400, C140, D410, D840, E740, F480, X450, X640, SGH-T499Y...)
In product numbers and serial numbers, the number 4 is removed.
Instead of using the number "Z4" worldwide, Sony used the number "Z3+" instead, probably because of tetraphobia in tetraphobic countries.
The British Medical Journal reported in a study that looked at mortality statistics in the United States over a 25-year period. They found that on the fourth day of the month, Asian people were thirteen percent more likely to die of heart failure. In California, Asians were twenty-seven percent more likely to die of a heart attack on that day. The purpose of the study was to see if psychological stress caused by belief in this superstition could indeed trigger deadly heart attacks and other fatal incidences.
- Numbers in Chinese culture
- Thirteenth floor
- Triskaidekaphobia (the fear of the number 13)
- Curse of 39
- Faux pas derived from Chinese pronunciation
- List of phobias
- τετράς, Henry George Liddell, Robert Scott, A Greek-English Lexicon, on Perseus
- φόβος, Henry George Liddell, Robert Scott, A Greek-English Lexicon, on Perseus
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- Floor plan remarks of Vision City
- Floor plan of The Arch
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- Media related to Tetraphobia at Wikimedia Commons