四捨五入
ししゃごにゅう · shishagonyuu · JLPT N2 · noun
rounding up (fractions)
Round to the nearest: shi-sha-go-nyuu sounds like 'shi-sha go new' (4-5 rounding up)
四捨五入: 四 (shi, 4) is dropped, 五 (go, 5) is the cutoff that pushes the number up. Read as: 'shi' = four, 'go' = five, and five means carry up.
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.
五 — two horizontal lines + crossed strokes
五 originally depicted two parallel lines (heaven and earth) with an X between them, representing the interaction of the five elements. Over time it became the standard numeral for 'five.' The ancient form 㐅 (just the X) was later framed by the two lines to distinguish it clearly as a number.
入 — single pictograph, two slanting strokes
入 is a pictograph showing an arrowhead or pointed entrance, with two strokes converging downward to suggest something going inward. The original sense was 'to enter,' and it still carries that meaning today. It contrasts visually with 人 (person), where the strokes cross differently at the top.