Across |

2. | When the sum of two angles is 180 degrees |

5. | Common endpoint of an angle |

6. | An angle that measures 90 degrees |

7. | A part of a line or ray that goes from one point to another |

9. | Lines that do not intersect that are in different planes |

10. | Part of a line that has one endpoint and extends in one direction |

12. | Angles that are opposite and formed by two intersecting lines |

14. | Figures that have same shape and size |

16. | When the sum of two angles is 90 degrees |

18. | Angles that have a common vertex and a common side |

19. | A flat surface that extends forever |