Angle facts for kids
An angle is formed when two straight lines meet at a point. These lines are called the sides of the angle. The point where they meet is called the vertex. You can also think of an angle as the amount of turn or space between these two lines.
Angles are often shown using Greek letters like 
(alpha), 
(beta), 
(gamma), and 
(theta).
We measure the size of an angle using units called degrees. The symbol for degrees is °. For example, 90° means 90 degrees. A degree can be broken down into smaller parts. One degree (1°) is equal to 60 minutes (60'). One minute (1') is equal to 60 seconds (60"). So, 22.5°, 221⁄2°, and 22° 30' all show the same angle.
In mathematics, angles can also be measured in radians. This is another way to measure angles, often used in higher math. For example, 360° is the same as 
radians. Another unit is the gradian, where 100 gradians equals 90°.
Angles are a big part of geometry. For example, a triangle has three sides, and two sides meet at each of its three corners (also called vertices). A cube has twelve edges, and three edges meet at each of its eight corners.
Types of angles
Angles have different names depending on their size:
- A zero angle is 0°. The lines lie exactly on top of each other.
- An acute angle is greater than 0° but less than 90°. It looks "sharp."
- A right angle is exactly 90°. It looks like the corner of a square.
- An obtuse angle is greater than 90° but less than 180°. It looks "wide."
- A straight angle is exactly 180°. It forms a straight line.
- A reflex angle is greater than 180° but less than 360°. It's the "outside" part of an angle.
- A full or complete angle is exactly 360°. It means you've made a full circle.
Angle relationships
Sometimes, angles are related to each other:
- Supplementary angles are two angles that add up to 180°.
- complementary angles are two angles that add up to 90° (a right angle).
- Explementary angles (or conjugate angles) are two angles that add up to 360° (a full circle).
People usually use a protractor to measure and draw angles. A protractor is a tool, often shaped like a half-circle or full circle, with degree markings.
Related pages
Images for kids
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An angle formed by two rays meeting at a vertex.
See also
In Spanish: Ángulo para niños
