Acute Angle

An angle with a measure greater than 0^{0} and less than 90^{0}.

Right Angle

An angle with a measure of 90^{0}.

Obtuse Angle

An angle with a measure greater than 90^{0} but less than 180^{0}.

Straight Angle

An angle with measure of 180^{0}.

Vertical Angle

Two pairs of opposite angles formed by two intersecting lines.

Adjacent Angle

Two angles that have the same vertex, share a common side, and do not overlap.

Complementary Angle

Two angles that have a sum of their measures as 90^{0}.

Supplementary Angle

Two angles that have a sum of their measures as 180^{0}.

Parallel Lines

Two lines in the same plane that do not intersect.

Transversal

A line that intersects two parallel sides.

Corresponding Angles

Angles that have the same position on two different parallel lines cut by a transversal.

Alternate Interior Angles

Nonadjacent interior angles found on opposite sides of the transversal.

Alternate Exterior Angles

Nonadjacent exterior angles found on opposite sides f the transversal.

Consecutive Interior Angles

When two lines are cut by a transversal, the pair of angles on one side of the transversal and inside the two lines.

Triangle

A figure having three sides

Equilateral Triangle

A triangle with all sides congruent.

Isosceles Triangle

A triangle with two sides congruent.

Scalene Triangle

A triangle with no sides congruent.

Right Triangle

A triangle with one right angle.

Legs

The sides that are adjacent to the right angle of a right triangle.

Hypotenuse

The side opposite the right angle in a right triangle.

Pythagorean Theorem

If a triangle is a right triangle, then the square of the length of the hypotenuse is equal to the sum of the squares of the lengths of the legs.

Quadrilateral

A closed figure with four sides and four vertices.

Parallelogram

A quadrilateral with opposite sides parallel and congruent.

Rhombus

A parallelogram with four congruent sides.

Rectangle

A parallelogram with four right angles.

Square

A parallelogram with all sides congruent and four right angles.

Trapezoid

A quadrilateral with exactly one pair of parallel sides.

Isosceles Trapezoid

A figure in which non-parallel sides and base angles are of the same measure.

Polygon

A simple closed figure in a plane formed by three or more line segments.

Sum Interior Angles of Polygon

(n - 2) * 180

Transformation

A movement of a geometric figure.

Reflection

A transformation where a figure is flipped over a line.

Line of Reflection

An image will reflect through a line.

Translation

A transformation where a figure is slide from one position to another without being turned.

Rotation

A transformation where a figure is turned around a fixed point.

Dilation

A transformation that alters the size of a figure but not its shape.

Scale Factor

The ratio of a length on a scale drawing or model to the corresponding length on the real object.

Similar Figures

Figures that have the same shape but not necessarily the same size.