Definition: An angle whose measure is greater than 180° and less than 360°

Try this
Adjust the angle below by dragging an orange dot and see how the angle ∠ABC behaves.
Note that it is a reflex angle only when it is between 180° and a full circle.

Some might argue than reflex angles are not real. They are the 'other half' of a smaller angle. Indeed if you refer to the angle ∠ABC without qualifying it,it is generally assumed that you mean the smallest angle. If you mean the large part of the angle, you must specify it by saying 'reflex angle ∠ABC'.

Altogether, there are six types of angle as listed below. Click on an image for a full description of that type and a corresponding interactive applet.

Acute angle Less than 90° |
Right angle Exactly 90° |
Obtuse angle Between 90° and 180° |

Straight angle Exactly 180° |
Reflex angle Between 180° and 360° |
Full angle Exactly 360° |

- Vertical angles
- Complementary angles
- Supplementary angles
- Linear pair
- Adjacent angles
- Corresponding angles
- Alternate interior angles
- Alternate exterior angles
- Interior angles of a transversal
- Exterior angles of a transversal

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