There are five basic types of angles, based on angle measurements. These measurements center around a right, or 90º angle. 90º angles look like an L; they form a perfect corner, like the corner on a piece of paper.

**Acute Angle**: an angle that measures less than 90º (think of “a cute little angle”)**Right Angle**: an angle that measures exactly 90º**Obtuse Angle**: an angle that measures more than 90º**Straight Angle**: an angle that measures exactly 180º (a straight line)**Reflex Angle**: an angle that measures more than 180º

There are two pairs of angles that have special properties:

**Complementary Angles**: angles that add up to 90º**Supplementary Angles**: angles that add up to 180º

In the example, angles 1 & 2 are complementary, and angles 3 & 4 are supplementary.

When angles are drawn by crossing lines we also create vertical angles.

**Vertical Angles**: angles that share the same vertex and are created by the same lines.

In the example, angles 2 & 3 are vertical because they have the same vertex and the same lines.

Another type of angle are adjacent angles.

**Adjacent Angles**: angles right next to each other, sharing a ray between them.

In the example, angles 1 & 2, and 3 & 4 are adjacent.