Explore Words Kanji Grammar Guides

Copyright © 2026 Kotomora. All Rights Reserved.

Get the Kotomora apps for iOS and Android.

Explore Words Kanji Grammar Guides About Support Privacy

Copyright © 2026 Kotomora. All Rights Reserved.

直径 (ちょっけい, chokkei) Japanese meaning: diameter | Kotomora

直ちょっ径けい

ちょ

っ

け

い

Common word›JLPTN2›Freq.FrequencyTop 10,000

Meanings

1

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

この円えんの直ちょっ径けいは10センチです。

The diameter of this circle is 10 centimeters.

直ちょっ径けいを測はかってください。

Please measure the diameter.

Usage patterns

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.

Kanji

直straightaway, honesty, frankness
径diameter, path, method

Related words

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.

Opposites

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).

Don't confuse with

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.

Word family

視し直ちょっ径けい
apparent diameter
共きょう役えき直ちょっ径けい対たい
conjugate diameter pair; CDP

Etymology

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