acute triangle | A triangle with three angles that each measure between 0º and 90º. |

congruent | Having the same size and shape. |

corresponding angles | Angles of separate figures that are in the same position within each figure. |

corresponding sides | Sides of separate figures that are opposite corresponding angles. |

equilateral triangle | A triangle with 3 equal sides. |

isosceles triangle | A triangle with 2 equal sides. |

obtuse triangle | A triangle with one angle that measures between 90º and 180º. |

polygon | A closed plane figure with three or more straight sides. |

right triangle | A triangle containing a right angle. |

scalene triangle | A triangle in which all three sides are a different length. |

similar | Having the same shape but not necessarily the same size. |

triangle | A polygon with three sides. |