Basic Geometry Terms

Front

Parallel Lines

Back

Lines in a plane that do not meet; they are always the same distance apart.

Front

Perpendicular Lines

Back

Lines that intersect at a 90-degree angle.

Front

Acute Angle

Back

An angle that is less than 90 degrees.

Front

Obtuse Angle

Back

An angle that is more than 90 degrees but less than 180 degrees.

Front

Right Angle

Back

An angle that is exactly 90 degrees.

Front

Vertical Angle

Back

Angles opposite each other when two lines cross. They are always equal.

Front

Complementary Angle

Back

Two angles whose measures add up to 90 degrees.

Front

Supplementary Angle

Back

Two angles whose measures add up to 180 degrees.

Front

Alternate Interior Angles

Alternate Exterior Angles

Back

When you have two parallel lines cut by a transversal, alternate interior/ exterior angles are inside/ outside the parallel lines and on opposite sides of the transversal. The angles are congruent

Front

Corresponding Angles

Back

When you have two parallel lines cut by a transversal, corresponding angles are angles that are in the same position.

These angles are congruent.