Early ways of writing four include 亖 (sì), four horizontal strokes. The familiar 四 (sì) has a different graphic history. Its enclosure should not be treated as a literal drawing of the four seasons.

The Shuowen Jiezi calls four a yin number and explains it within a correlative system. Such dictionary explanations tell us how later scholars understood a character; they are not always descriptions of its earliest invention.

East, south, west and north organize space; spring, summer, autumn and winter organize the year. 四方 (sì fāng) and 四时 (sì shí) can therefore evoke completeness. 四海 (sì hǎi, the four seas) is often a literary expression for the whole known world, not a precise list of four named bodies of water.

The four celestial emblems place the Azure Dragon in the east, the Vermilion Bird in the south, the White Tiger in the west and the Dark Warrior—usually a tortoise entwined with a snake—in the north. Their astronomical and seasonal associations developed over time.

Grouping things in fours makes knowledge easy to carry in memory. Some familiar lists are old textual classifications; others are later selections that became widely accepted. The “Four Great Towers,” for example, have more than one popular list.

A 四合院 (sì hé yuàn) gathers buildings around a courtyard. Its practical arrangement offers an image of an enclosed, shared household. 四世同堂 (sì shì tóng táng), four generations under one roof, expresses another family ideal, even when actual living arrangements differ.

Celebratory language gathers four happy occasions: rain after a long drought, meeting an old friend far from home, a wedding night and success in the examinations. Four happiness meatballs, 四喜丸子 (sì xǐ wán zi), bring festive completeness to the table; explanations of their four blessings vary.

Dates, peanuts, longans and lotus seeds can be combined as wedding wordplay wishing for children. Local “four red” clothing customs also occur. They should not be confused with a universal four-stage wedding ritual: the classical marriage sequence is usually described as six rites, not the first four rites alone.

The older “four virtues” prescribed for women record historical expectations about conduct, speech, appearance and work. Presenting them accurately requires recognizing the restrictions of that social order.

四 (sì) resembles 死 (sǐ, death) in Mandarin, and related sound associations occur in other Chinese varieties. Avoidance of four in room numbers or gifts coexists with positive four-part traditions. Neither response represents every Chinese speaker, and the taboo has no single simple origin.

Buddhist 四大 (sì dà) refers to earth, water, fire and wind as qualities of material existence. Saying that they are “empty” concerns their lack of independent, permanent nature; it is not simply the assertion that nothing exists. Traditional medicine also relates four-season changes to the body, while 四肢 (sì zhī) is the everyday expression for the four limbs.