In Geometry, adjacent angles share a line and a vertex. Therefore, they must possess both qualities to make them equal grades. You can see this represented in the diagram below.
This diagram clarifies why they are called adjacent angles – they are next to each other.
Complementary angles and supplementary angles
In Geometry, adjacent angles can sometimes also be either complementary or supplementary. Complementary means the two values of the angles will add up to 90 degrees, resulting in a right angle.
Supplementary angles add up to 180 degrees, meaning that the sum also makes up a line. These adjacent angels have two lines in common.
