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Mathematics vocabulary · Geometry

Radius

Meaning in mathematics, with examples

/ˈreɪdiəs/nounCore term

In mathematics, radius means: The distance from the centre of a circle or sphere to any point on its edge; it is half the diameter.

In Turkish: yarıçap

How it is used

Used in formulas such as the area of a circle, πr², and its circumference, 2πr. You find, measure or are given the radius. In geometry problems the letter r almost always stands for the radius.

Example sentences

  1. A circle has a radius of 6 cm. Find its circumference.

  2. If you double the radius, the area becomes four times larger.

Common collocations

  • radius of a circle
  • radius of the sphere
  • radius r
  • given radius
  • diameterA straight line from one side of a circle or sphere to the other through its centre, or the length of this line, which is twice the radius.
  • areaThe size of a flat surface, measured in square units such as cm² or m²; a rectangle 4 m long and 3 m wide has an area of 12 m².
  • perimeterThe total length of the boundary of a flat shape; for a rectangle 5 cm long and 3 cm wide, the perimeter is 16 cm.
  • volumeThe amount of space a solid object takes up or a container holds, measured in cubic units such as cm³ or m³.

More terms: Geometry

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