Definition
Angle measure
Angle measure is the size of the turn between two rays, usually written in degrees.
What it means
Imagine one ray turning around the point where the rays meet until it lies on the other ray. Angle measure tells how big that turn is. Degrees split one full turn into 360 equal tiny turns. Look at the opening or turn, not at how long the rays are drawn.
Remember it
Measure the turn at the vertex, not the length of the arms.
Example
A 60° angle makes one sixth of a full turn because 360° ÷ 6 = 60°. Extending either ray makes the drawing larger, but the turn stays 60°, so the angle measure does not change.
Watch for
Making one ray longer without rotating it is not a change in angle measure.
Common mix-up
An angle is the figure made by two rays. Its angle measure is the number and unit that tell the size of the turn, such as 60°.
Exact meaning
Angle measure is the amount of rotation from one ray to another about their shared endpoint. A degree is 1/360 of a full turn, so an angle measuring n degrees contains n one-degree turns. Changing only the rays’ lengths does not change the angle measure.