直径
zhí jìng · HSK 7
diameter
⭕ 直 straight + 径 path = the straight path across a circle = diameter
直 means straight and 径 means a path or track; a diameter is the straight path cutting through the centre of a circle from edge to edge. Contrast with 半径 (half + path) which is the radius.
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.'