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Acute Angle

An angle that measures less than 90 degrees

Adjacent Angles

Angles in the same plane that have a common vertex and a common side

Angle

A figure formed by two rays with a common endpoint called the vertex

Area

The number of square units needed to cover a given surface

Average

The sum of the items in a set of data divided by the number of items in the set; also called mean

Circle

The set of all points in a plane that are the same distance from a given point called the center

Circumference

The distance around a circle

Clustering

A method used to estimate a sum when all addends are close to the same value

Complementary Angles

Two angles whose measures add to 90 degrees

Composite Number

A number greater than 1 that has more than two whole-number factors

Congruent

Having the same size and shape

Cross Product

The product of numbers on the diagonal when comparing two ratios

Customary System

The measurement system often used in the United States

Denominator

The bottom number of a fraction that tells how many equal parts are in the whole

Diameter

A line segment that passes through the center of a circle and has endpoints on the circle, or the length of that segment

Difference

The result when one number is subtracted from another

Dividend

The number to be divided in a division problem

Divisible

Can be divided by a number without leaving a remainder

Divisor

The number you are dividing by in a division problem

Endpoint

A point at the end of a line segment or ray

Expanded Form

A number written as the sum of the values of its digits

Exponent

The number that indicates how many times the base is used as a factor

Factor

A number that is multiplied by another number to get a product

GCF (Greatest Common Factor)

The largest common factor of two or more given numbers

Improper Fraction

A fraction in which the numerator is greater than or equal to the denominator

Indirect Measurement

The technique of using similar figures and proportions to find a measure

Integer

A member of the set of whole numbers and their opposites

Intersecting Lines

Lines that cross at exactly one point

Interval

The space between marked values on a number line or the scale of a graph

Inverse Operations

Operations that undo each other: addition and subtraction, or multiplication or division

LCD (Least common denominator)

The least common multiple of two or more denominators

LCM (Least common multiple)

The smallest number, other than zero, that is a multiple of two or more given numbers

Like Fractions

Fractions that have the same denominator

Line

A straight path that extends without end in opposite directions

Line of Reflection

A line that a figure is figure is flipped across to create a mirror image of the original figure

Line of Symmetry

The imaginary "mirror" in line symmetry

Mean

The sum of the items in a set of data divided by the number of items in the set; also called average

Median

The middle number or the mean (average) of the two middle numbers in an ordered set of data

Metric System

A decimal system of weights and measures that is used universally in science and commonly throughout the world

Mixed Number

A number made up of a whole number that is not zero and a fraction

Mode

The number or numbers that occur most frequently in a set of data; when all numbers occur with the same frequency, we say there is no mode

Multiple

A multiple of a number is the product of the number and any nonzero whole number

Negative Number

A number less than zero

Net

An arrangement of two-dimensional figures that can be folded to form a polyhedron

Numerator

The top number of a fraction that tells how many parts of a whole are being considered

Obtuse Angle

An angle whose measure is greater than 90 degrees but less than 180 degrees

Odd Number

A whole number that is not divisible by two

Opposites

Two numbers that are an equal distance from zero on a number line

Order of Operations

A rule for evaluating expressions: first perform the operations in parentheses, then compute powers and roots, then perform all multiplication and division from left to right, and then perform all addition and subtraction from left to right

Parallel Lines

Lines in a place that do not intersect

Percent

A ratio comparing a number to 100

Perimeter

The distance around a polygon

Perpendicular Lines

Lines that intersect to form right angles

Pi

The ratio of the circumference of a circle to the length of its diameter; 3.14 or 22/7

Plane

A flat surface that extends forever

Point

An exact location in space

Polygon

A closed plane figure formed by three or more line segments that intersect only at their endpoints

Polyhedron

A three-dimensional figure in which all the surfaces or faces are polygons

Positive Number

A number greater than zero

Prime Factorization

A number written as the product of its prime factors

Prime Number

A whole number greater than 1 that has exactly two factors, itself and 1

Prism

A polyhedron that has two congruent, polygon-shaped bases and other faces that are all rectangles

Product

The result when two or more numbers are multiplied

Proportion

An equation that states that two ratios are equivalent

Protractor

A tool for measuring angles

Pyramid

A polyhedron with a polygon base and triangular sides that all meet at a common vertex

Quadrant

The x- and y-axes divide the coordinate plane into four regions. Each region is called a quadrant.

Quotient

The result when one number is divided by another

Radius

A line segment with one endpoint at the center of a circle and the other endpoint on the circle, or the length of that segment

Range

The difference between the greatest and least values in a data set

Rate

A ratio that compares two quantities measured in different units

Ratio

A comparison of two quantities by division

Reciprocal

One of two numbers whose product is 1

Reflection

A transformation of a figure that flips the figure across a line

Regular Polygon

A polygon with congruent sides and angles

Rotation

A transformation in which a figure is turned around a point

Scientific Notation

A method of writing very large or very small numbers by using powers of 10

Similar

Figures with the same shape but not necessarily the same size are similar

Skew Lines

Lines that lie in different planes that are neither parallel nor intersecting

Straight Angle

An angle that measures 180 degrees

Sum

The result when two or more numbers are added

Supplementary Angles

Two angles whose measures have a sum of 180 degrees

Surface Area

The sum of the areas of the faces, or surfaces, of a three-dimensional figure

Transformation

A change in the size or position of a figure

Translation

A movement (slide) of a figure along a straight line

Variable

A symbol used to represent a quantity that can change

Vertex

On an angle or polygon, the point where two sides intersect

Vertical Angles

A pair of opposite congruent angles formed by intersecting lines

Volume

The number of cubic units needed to fill a given space

Zero Pair

A number and its opposite, which add to 0