The unlucky numbers: 4 and 9
Japan's most significant number taboo involves 四 (4, shi) and 九 (9, ku). The problem is sound: 四 pronounced shi is homophonous with 死 (death). 九 pronounced ku sounds identical to 苦 (suffering, hardship). As a result, many Japanese hospitals have no room 4, buildings skip the 4th floor, and gifts of four items are considered inappropriate — particularly for the ill.
The avoidance runs deep. Japanese phone numbers, car registration plates, and product serial numbers often substitute alternate readings (yon for 4, kyuu for 9) to sidestep the associations.
Lucky numbers: 7, 8, and 3
七 (7, shichi/nana) is considered lucky — Japan has 七福神 (the Seven Lucky Gods), 七五三 (the Shichi-Go-San children's festival), and 七夕 (the Tanabata star festival). Eight (八, hachi) is lucky because the kanji 八 widens at the bottom, suggesting growing prosperity. Three (三) appears in many auspicious groupings: 三種の神器 (the three imperial treasures), 三つ葉 (three-leaf clover).
In some Japanese regions, 42 (四十二) is considered doubly unlucky — it can be read as shi-ni, meaning "to die." Similarly, 43 (shi-san) can sound like "stillbirth." These combinations are avoided in hospital room numbering, parking lots, and product numbering throughout Japan.
Numbers in daily Japanese life
The cultural weight of number associations shows up constantly: gift sets come in threes, fives, or sevens — never fours. Wedding speeches avoid the words 切る (cut) and 終わる (end), and numbers associated with those concepts. Apartment listings in Japan sometimes note the absence of 4th-floor rooms as a selling point. Number beliefs are not superstition at the margins — they are woven into the fabric of everyday decision-making.