The World of Angles
Study how angles are formed, how they are measured, and how angle pairs behave when lines or rays meet.
14 concepts in this topic
These pages connect angle vocabulary to visible turning, degree measure, and position in the diagram, so angle rules feel easier to read and use.
Parts of an Angle
An angle is made from a vertex and two sides that are rays.
Acute Angle
An acute angle measures less than 90 degrees.
Right Angle
A right angle measures exactly 90 degrees.
Obtuse Angle
An obtuse angle measures more than 90 degrees and less than 180 degrees.
Straight Angle
A straight angle measures exactly 180 degrees.
Reflex Angle
A reflex angle measures more than 180 degrees and less than 360 degrees.
Full Rotation
A full rotation measures 360 degrees.
Adjacent Angles
Adjacent angles share a common vertex and side without overlapping interiors.
Complementary Angles
Complementary angles add to 90 degrees.
Supplementary Angles
Supplementary angles add to 180 degrees.
Linear Pair
A linear pair is a pair of adjacent supplementary angles.
Vertical Angles
Vertical angles are opposite angles formed by two intersecting lines.
Congruent Angles
Congruent angles have equal measure.
Angle Bisector
An angle bisector divides an angle into two equal angles.