Labels for the different parts of a circle are given below

Radius – the radius of a circle is the distance from the centre labelled O to the circumference. The radius is labelled | |

The circumference of a circle is the perimeter, and is labelled | |

Diameter – diameter of a circle is the length of a straight line between opposite ends drawn through the centre. The diameter is labelled and is equal to | |

Tangent – A straight line drawn outside the circle which just touches it. | |

Chord - a line (not through the centre) drawn between any two points on the circumference. | |

Arc – a part of the circumference. The length of an arc iswhereis the radius andis the angle in radians. | |

Sector - the part of a a circle between two radii and an arc. We can divide a circle into major and minor sectors. The area of a sector iswhereis the angle in radians. | |

Segment - the part of a a circle between chord and an arc. We can divide a circle into major and minor segments. The area of the minor segment on the right iswhereis in radians. | |