直径

• Pinyin: zhí jìng
• Hanzi breakdown: 直 = straight; 径 = 彳 + 圣 (path — a direct route)

Meaning

Diameter; the straight line passing through the centre of a circle connecting two points on its circumference.

A mathematical and technical term. Used in geometry, engineering, and everyday measurement. Contrasted with 半径 (radius) and 周长 (circumference). Also used figuratively for something's span or reach.

Examples

1. 这个水管的直径是五十毫米，足够满足供水需求。 The pipe’s diameter is 50 millimeters, which is enough to meet the water-supply needs.
2. 月球的直径约为地球直径的四分之一。 The moon’s diameter is about one-quarter of Earth’s.
3. 工程师测量了轴承的直径，确认规格符合设计要求。 The engineer measured the bearing’s diameter to confirm the specs met the design requirements.

Usage Guide

Context: mathematics, engineering, measurement

Tone: technical

Do Say

• 请计算出这个圆的直径和面积。(Please calculate the diameter and area of this circle.)
• 这条隧道直径达到十五米，是亚洲最大的盾构隧道之一。(This tunnel has a diameter of fifteen metres and is one of the largest shield tunnels in Asia.)

Don't Say

• 这个正方形的直径 — squares have 对角线 (diagonal), not 直径; diameter is only for circles and spheres

Origin & History

直 (straight) + 径 (path/line) — the straight path through the centre

Cultural Context

Generation: All ages

Social background: Universal