diameter

Everyday

1. A straight line going from one side of a circle to the other, passing through the centre. tree →
2. The length of that line; how wide a circle or round thing is. tree →

In the lessons

In maths lessons, the diameter is twice the radius, and the circumference is about 3.14 (pi) times the diameter. In science and everyday life, the diameter of a pipe, a wheel or a planet tells its width. Phrases: in diameter.

Examples

• The diameter of the circle is 10 cm. tree →
• The radius is half the diameter. tree →
• The Earth's diameter is about 12,700 km. tree →
• Measure the diameter of the pizza. tree →
• The pipe is 5 cm in diameter. tree →
• The circumference is pi times the diameter. tree →
• She was three feet and a half in diameter, and made of the very best gunpowder. tree →

Note

In maths problems: diameter = 2 × radius; radius = diameter ÷ 2; circumference = π × diameter (about 3.14 × d). Do not confuse with «perimeter».

In Jewish tradition

In maths lessons, the diameter is twice the radius, and the circumference is about 3.14 (pi) times the diameter. In science and everyday life, the diameter of a pipe, a wheel or a planet tells its width. Phrases: in diameter.

Note

In maths problems: diameter = 2 × radius; radius = diameter ÷ 2; circumference = π × diameter (about 3.14 × d). Do not confuse with «perimeter».