Properties of Circles

  • Center – A point inside the circle. All points on the circle are equidistant (same distance) from the center point.
  • Radius - The radius is the distance from the center to any point on the circle. It is half the diameter.
  • Diameter - The distance across the circle. The length of any chord passing through the center. It is twice the radius.
  • Circumference - The circumference is the distance around the circle.
  • Area - Strictly speaking a circle is a line, and so has no area. What is usually meant is the area of the region enclosed by the circle.
  • Chord - A line segment linking any two points on a circle.
  • Tangent - A line passing a circle and touching it at just one point.
  • Secant - A line that intersects a circle at two points.