noun
Technical term used in geometry and measurement; refers to the total length around a closed shape.
この長方形の周囲長を計算してください。
Please calculate the perimeter of this rectangle.
円の周囲長は直径に円周率をかけて求めます。
The circumference of a circle is found by multiplying the diameter by pi.
円周 specifically means circumference of a circle, while 周囲長 can refer to the perimeter of any shape.
Compound of 周囲 (shūi, 'surroundings; circumference') and 長 (chō, 'length'). The reading is on'yomi throughout.