diameter · path

1. Origins, structure, and basic meaning

• Structure: 径 has 8 strokes and the on-reading けい. 直径 (ちょっけい) means diameter, and 半径 (はんけい) means radius.
• Basic usage: 直径 is the distance across a circle through its center; 半径 is the distance from the center to its edge.

2. Common pitfalls and similar expressions

• Diameter and radius
  • 直径が二十センチある means that the diameter is twenty centimeters. 直径 is read ちょっけい, including a small っ.
  • 半径三センチの円 means a circle with a radius of three centimeters. 駅を中心に半径一キロの範囲 identifies an area within a one-kilometer radius of the station.