A | B |

radius | line segment from center to any point of a circle |

diameter | a chord that passes through the center of a circle |

chord | line segment with end points on a circle |

circle | all the points in a plane the same distance from a given point |

compass | tool for drawing a circle |

angle | two rays with a common end point |

right angle | 90° angle |

acute angle | less than 90° angle |

obtuse angle | greater than 90° angle |

protractor | tool for making and measuring angles |