This cultural superstition can be considered a form of tetraphobia.

In Korea, tetraphobia is not as important, but the floor number 4 is almost always left out in hospitals.

See tetraphobia and Numbers in Chinese culture.

The notion in "Tom's Divorce" that the fourth floor refers to tetraphobia, the superstitious fear of the number four.

Immediately above 39/F is 50/F, leading many who do not know about tetraphobia to think that some floors are missing.

See tetraphobia.

A Psion Series 4 does not exist, due to Psion's concern of tetraphobia in their Asian markets.

The buses were registered in the license plate range SBS7500D to SBS7686B excluding registration numbers containing the digit 4 (due to tetraphobia).

Nokia decided to jump directly from S60 3rd Edition to S60 5th Edition, skipping the fourth edition due to the tetraphobia of their Asian customers.

Some of the registration series for the second batch of buses, however, does not include those ending with the number 'four' for buses registered after 9 June 2008 (due to tetraphobia).

Upon closer examination, the phone is displaying an incoming call from the number 4444444444 (the numeral "4" is symbolic of bad luck in many Asian cultures, a phenomenon that is known as tetraphobia.)

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.

In the mid-1990s, the rapidly growing CMMS, Maximo, moved from Maximo Series 3 directly to Series 5, skipping Series 4 due to that number's perceived marketing difficulties in the Chinese market, where the number 4 is associated with "death" (see tetraphobia).