Circle - Terminology

Terminology

• Chord: a line segment whose endpoints lie on the circle.
• Diameter: the longest chord, a line segment whose endpoints lie on the circle and which passes through the centre; or the length of such a segment, which is the largest distance between any two points on the circle.
• Radius: a line segment joining the center of the circle to any point on the circle itself; or the length of such a segment, which is half a diameter.
• Circumference: the length of one circuit along the circle itself.
• Tangent: a straight line that touches the circle at a single point.
• Secant: an extended chord, a straight line cutting the circle at two points.
• Arc: any connected part of the circle's circumference.
• Sector: a region bounded by two radii and an arc lying between the radii.
• Segment: a region bounded by a chord and an arc lying between the chord's endpoints.