直ちょっ径けい

ちょ

っ

け

い

Common wordJLPTN2Freq.FrequencyTop 10,000

Meanings

1

Standard mathematical and everyday term for the diameter of a circle or sphere.

直ちょっ径けいを測はかってください。

Please measure the diameter.

直ちょっ径けい〈数すう〉センチa diameter of ~ centimeters
このボールは直ちょっ径けい10センチです。
This ball is 10 centimeters in diameter.
直ちょっ径けいを測はかるto measure the diameter
コンパスを使つかって円えんの直ちょっ径けいを測はかった。
I measured the circle's diameter using a compass.
直ちょっ径けい〈数すう〉の〈物もの〉an object with a diameter of ~
直ちょっ径けい30センチのパイプを使つかう。
We use a pipe with a 30-centimeter diameter.

径けい
直径 is the everyday, unambiguous word for 'diameter', while 径 is a shorter, more technical form often used in compounds or scientific writing.
口こう径けい
口径 specifically means the inner diameter of a tube, gun barrel, or lens, while 直径 is the general term for the diameter of any circle or cylinder.

半はん径けいN2
半径 is the distance from the center to the edge of a circle, while 直径 is the full distance across through the center (twice the 半径).

半はん径けいN2
直径 is the full diameter of a circle, while 半径 is the radius, exactly half that length, and the two terms are easy to mix up when translating.
円えん周しゅうN2
直径 refers to the straight-line width of a circle, whereas 円周 is the curved distance around it, so learners sometimes confuse which measurement each word describes.

From 直 (straight) and 径 (path, diameter). The reading ちょっけい is the on'yomi of the kanji.