直角
ちょっかく · chokkaku · JLPT N2 · noun
right angle
📐 直 (straight) + 角 (corner) = a corner that is perfectly straight, at 90 degrees
直 means straight or direct, and 角 means corner or angle (it also means horn). Together they name a corner whose sides meet straight across.
直 — 十 ten + 目 eye + 乚 hidden line
Originally depicted an eye (目) looking straight along a vertical line, suggesting a direct, unswerving gaze. The form combines 目 'eye' with strokes indicating straightness. From this came the meanings 'straight,' 'upright,' and by extension 'honest' or 'direct.'
角 — pictograph of a horn
角 is a pictograph of an animal's horn, with early oracle-bone forms clearly showing the curved, ridged shape of a horn. From 'horn' it extended to mean corner, angle, and by metaphor a role or part (as in a stage role). The reading jiǎo covers most of these senses.