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- A circle is a shape consisting of all points in a plane that is a given distance from a given point, the centre; i.e
**it is the curve drawn out by a point**that moves in a plane so that its distance from a given point is constant.

Some of **real-world examples** are: Cycle wheels, round cake, bangles, round pizza, Coins etc

After knowing the concept of circle let’s get into some of **the important Terminology of the circle:**

Term |
Definition |

Annulus | a ring-shaped object, the region bounded by two concentric circles. |

Arc | any connected part of a circle. Specifying two endpoints of an arc and a centre allows for two arcs that together make up a full circle. |

Centre | the point equidistant from all points on the circle. |

Chord | a line segment whose endpoints lie on the circle, thus dividing a circle into two segments. |

Circumference | the length of one circuit along the circle, or the distance around the circle. |

Diameter | a line segment whose endpoints lie on the circle and that passes through the centre |

Disc | the region of the plane bounded by a circle. |

Radius | a line segment joining the centre of a circle with any single point on the circle itself |

Sector | a region bounded by two radii of equal length with a common center and either of the two possible arcs, determined by this center and the endpoints of the radii. |

Segment | a region bounded by a chord and one of the arcs connecting the chord’s endpoints. The length of the chord imposes a lower boundary on the diameter of possible arcs. |

Secant | an extended chord, a coplanar straight line, intersecting a circle in two points. |

Semicircle | one of the two possible arcs determined by the endpoints of a diameter, taking its midpoint as centre. |

Tangent | a coplanar straight line that has one single point in common with a circle (“touches the circle at this point”). |

Above figures describe what exactly each terminology look like.

Now let us get into detailed concepts of each terminology of the circle starting with Perimeter and Area of a Circle.

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