直 径(ちょっけい)

ちょっけい

noun

diameter

1. diameter

A straight line passing through the center of a circle, connecting two points on the circumference.

この円(えん)の直径(ちょっけい)は10センチです。

The diameter of this circle is 10 centimeters.

直径(ちょっけい)は半径(はんけい)の2倍(ばい)だ。

The diameter is twice the radius.

直径(ちょっけい)30センチのピザを注文(ちゅうもん)した。

I ordered a pizza with a 30-centimeter diameter.

直径(ちょっけい) is the diameter - a line passing through the center of a circle connecting two points on the edge.

Writing

直(ちょく): straight, direct
径(けい): path, diameter

USAGE (formulas):

直径(ちょっけい) = 半径(はんけい) × 2 (diameter = radius × 2)
円周(えんしゅう) = 直径(ちょっけい) × π (circumference = diameter × π)
面積(めんせき) = π × (半径(はんけい))² (area formula)

Common expressions

直径(ちょっけい)〜センチ: ~ cm in diameter
直径(ちょっけい)を測(はか)る: to measure the diameter

Related words

Related Words

Related: 半径(はんけい) (radius)

Related: 円周(えんしゅう) (circumference)

Related: 円(えん) (circle)

Related: 球(きゅう) (sphere)

general

Added 2026.1.16 16:37 · Revised 2026.10.11 3:34

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