正方形
せいほうけい · seihoukei · JLPT N2 · noun
square
⬜ 正方形 = 正 (even) + 方 (side) + 形 (shape): a shape with equal sides
正 means even or true, and 方 here means side. So 正方形 is a shape whose sides are all even, meaning equal in length. A 長方形 (rectangle) has only opposite sides equal.
正 — one 一 + stop 止
Originally an ideograph showing a foot (止) advancing toward a target line (一), meaning 'to march straight toward' a city or goal. From this came the senses 'upright,' 'correct,' and 'proper.' The military sense survives in 征 (to campaign), which took over the original 'march' meaning.
方 — pictograph of a plow or two boats joined side by side
方 originated as a pictograph, traditionally interpreted as a plow handle or two boats lashed together. From the idea of paired boats it extended to mean 'side by side,' then 'square,' 'direction,' and 'region.' It was later borrowed for the abstract sense of 'method' or 'way.'
形 — open frame 开 + hair/pattern 彡
形 combines 开 (originally a phonetic element suggesting the sound) with 彡, a radical depicting fine lines, hair, or decorative strokes. The 彡 part conveys the idea of visible markings or surface appearance, giving 形 its core meaning of 'shape' or 'form.' Over time it broadened to cover physical figure, appearance, and abstract form.