四
sì · HSK 1
four
4️⃣ 四 originally showed nostrils breathing; later borrowed for the number four
The ancient form depicted a mouth or nostrils exhaling, but the character was phonetically borrowed to write the number four. The modern shape encloses two strokes inside a box, unrelated to its breath-origin.
四 — enclosure 囗 + divide 八
Originally 四 was written as four horizontal strokes (亖), a simple tally for the number four. The current form, showing 八 (divide) inside an enclosure 囗, was borrowed during the Zhou dynasty and gradually replaced the older tally form. The shape is unrelated to its meaning today.