# Symbols in Geometry

## Common Symbols Used in Geometry

Symbols save time and space when writing. Here are the most common geometrical symbols:

Symbol | Meaning | Example | In Words |
---|---|---|---|

Triangle | ABC has 3 equal sides | Triangle ABC has three equal sides | |

Angle | ABC is 45° | The angle formed by ABC is 45 degrees. | |

Perpendicular | ABCD | The line AB is perpendicular to line CD | |

Parallel | EFGH | The line EF is parallel to line GH | |

Degrees | 360° | 360 degrees (a full rotation!) | |

Right Angle (90°) | is 90° | A right angle is 90 degrees | |

Line Segment "AB" | AB | The line segment between A and B | |

Line "AB" | The infinite line that includes A and B | ||

Ray "AB" | The line that starts at A, goes through B and continues on | ||

Congruent (same shape and size) | ABC DEF | Triangle ABC is congruent to triangle DEF | |

Similar (same shape, different size) | DEFMNO | Triangle DEF is similar to triangle MNO | |

Therefore | a=b b=a | a equals b, therefore b equals a |

### Example: In ABC, BAC is

*Is really saying:* "In triangle ABC, the angle BAC is a right angle"

### Naming Angles

For angles the central letter is where the angle is.

### Example: ABC is 45°

The point "B" is where the angle is.