Geometry Basics – Vocabulary List

Front

Adjacent Angles

Back

Two angles that share a common side and vertex (are 'next to' each other).

Front

Vertical Angles

Back

Two angles directly across from each other on intersecting lines; they are always congruent.

Front

Complementary Angles

Back

Two angles whose measures have a sum of 90°; they do not have to be adjacent.

Front

Supplementary Angles

Back

Two angles whose measures have a sum of 180°; they do not have to be adjacent.

Front

Linear Pair

Back

Adjacent angles that are supplementary and form a straight line.

Front

Perpendicular

Back

Two lines that intersect at a 90° (right) angle.

Front

Angle Bisector

Back

A line or ray that divides an angle into two equal parts.

Front

Midpoint Formula

Back

A formula used to find the midpoint between two endpoints.

Front

Segment Bisector

Back

A segment, line, or plane that intersects a segment at its midpoint.

Front

Ray

Back

A line that extends indefinitely in one direction.