roundness

Everyday

1. The quality of being round or curved like a circle or ball. tree →
2. A full, smooth quality, for example of a sound or a taste. tree →

In the lessons

In maths, roundness is about circles, spheres and curves; a circle is perfectly round. In science and geography, the roundness of the Earth (it is close to a sphere) explains why ships seem to disappear over the horizon. In art, roundness makes a drawing look solid. Phrases: the roundness of the Earth, the roundness of her face.

Examples

• The roundness of the ball helps it roll. tree →
• The Earth's roundness was known to the ancient Greeks. tree →
• Pebbles get their roundness from being rolled by water. tree →
• The artist shaded the apple to show its roundness. tree →
• The roundness of the cello's sound was lovely. tree →
• We measured the roundness of each orange. tree →
• Even the moon is not always perfect in shape, but loses its roundness with time, and flowers bloom and then fade. tree →

Note

Uncountable. From "round" + -ness. The Earth is not perfectly round — it bulges a little at the equator. Myth: people in the Middle Ages did not all think the Earth was flat; educated people knew it was round.