Wiktionary
tetraphobia
n. Custom of avoiding the number four (4) commonly seen in East Asian countries in which the words for "4" and "death" are paronymous or homophonous.
Wikipedia
Tetraphobia
rowspan=2| Language
colspan=2|Reading
四
(four)
死
(death)
Mandarin Chinese
sì
Wu Chinese ( Shanghainese)
sy²
Cantonese
sei³
Hakka
si³
Min Nan ( Hokkien)
sì, sù
Vietnamese
tư, tứ
Korean
sa
Japanese
shi
Tetraphobia (from Greek τετράς—tetras, "four" and φόβος—phobos, "fear") is the practice of avoiding instances of the number . It is a superstition most common in East Asian nations.