When two lines meet at a common point (vertex) the angle between them is called the included angle. The two lines define the angle. So for example in the figure above we could refer to the angle ∠ABC as the "included angle of BA and BC".

Or we could refer to "BA and BC and their included angle".

See also Included side

Related angle topics

General

• Angle definition
• Degrees
• Radians
• Angle bisector
• Subtended angle
• Interior of an angle
• Included angle

Angle Types

• Acute angle
• Right angle
• Obtuse angles
• Straight angle
• Reflex angle
• Full angle

Angle relationships

• Vertical angles
• Complementary angles
• Supplementary angles
• Linear pair
• Adjacent angles
• Corresponding angles
• Alternate interior angles
• Alternate exterior angles
• Interior angles of a transversal
• Exterior angles of a transversal