What is an Angle?
The figure formed by two rays diverging from a common point. The amount of turn between the rays.
An angle is the shape made when two rays start at the same point and move in different directions. The common point where they meet is called the vertex, and the two rays are called the sides of the angle.
Think of it like opening a book: the spine is the vertex, and the pages spreading apart form the rays. The space between the pages is the angle.
An angle is also the measure of how much one side has turned relative to the other, and this turn is measured in degrees (°). A full turn is 360°, a half turn is 180°, a quarter turn is 90°.
The amount of turn between the rays (or sides) determines how big or small the angle is. We can use this information to classify angles into these common types:
- Right angle – exactly 90° (like the corner of a square)
- Acute angle – less than 90°
- Obtuse angle – more than 90° but less than 180°
- Straight angle – exactly 180°, forming a straight line
Angles are all around us! We use them in:
- Geometry and shapes (like triangles and polygons)
- Measuring turns and rotations
- Building and construction
- Navigating directions
- And more
When Do Students Learn About Angles?
Students start learning about angles in elementary school and deepen their understanding in middle school and beyond through geometry.
Grades 3–4 – Introduction to Angles
Students begin identifying angles, naming their parts (vertex and rays), and recognizing right, acute, and obtuse angles.
Grades 5–6 – Measuring and Classifying Angles
Students learn to use protractors, measure angles in degrees, and classify angles by size.
Grades 7+ – Applying Angles in Geometry
Students explore angle relationships, such as complementary, supplementary, and vertical angles, and use angles to solve problems involving triangles, polygons, and parallel lines.
