Illustrated math words

Math Dictionary

A bright, visual math vocabulary hub with quick definitions, examples, diagrams, common mistakes, and practice prompts for the terms students meet in class and on tests.

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Last updated: June 1, 2026
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The dictionary is built as a learning tool: every word connects a definition to an example, a visual, a common mistake, and practice.

Plain definitionShort, student-friendly wording before technical details get heavy.
Visual modelNumber lines, graphs, geometric sketches, and data displays where they help.
ExamplesConcrete math examples so students see the word in action.
Common mistakeThe exact misconception students often make with that term.
Try oneA quick practice prompt with an answer for immediate review.
Related termsInternal links that move students through connected vocabulary.

Guided Study Sets

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Complete Topic Index

Open any topic to see the full list of terms in that area.

Number System (25)
Algebra (23)
Geometry (20)
Functions (7)
Statistics (13)
Measurement (4)
Ratios and Proportions (7)
Problem Solving (5)

Grade Paths

Grade 3 (18)
Grade 4 (30)
Grade 5 (44)
Grade 6 (77)
Grade 7 (68)
Grade 8 (80)
Algebra 1 (56)
Algebra 2 (6)

Test Paths

GED (87)
SAT (82)
ACT (82)

A

Absolute Value

Absolute value is the distance of a number from 0 on the number line.

Try: What is |3 – 11|?
Number SystemGrade 6GED

Additive Inverse

An additive inverse is a number that adds with another number to make 0.

Try: What is the additive inverse of -14?
Number SystemGrade 6GED

Angle

An angle is formed by two rays that share the same endpoint.

Try: What is the measure of a right angle?
GeometryGrade 4GED

Area

Area measures the amount of flat space inside a two-dimensional shape.

Try: What is the area of a rectangle with length 8 and width 4?
GeometryGrade 3GED

B

Bar Graph

A bar graph uses bars to compare amounts in different categories.

Try: What should you check before comparing bar heights?
StatisticsGrade 3GED

Base

A base is the number or expression that is repeatedly multiplied when using an exponent.

Try: What is the base in 6^2?
AlgebraGrade 6GED

Binomial

A binomial is a polynomial with exactly two terms.

Try: Is 5x – 9 a binomial?
AlgebraAlgebra 1SAT

Box Plot

A box plot displays data using the minimum, first quartile, median, third quartile, and maximum.

Try: What value is shown by the line inside the box?
StatisticsGrade 6SAT

C

Centimeter

A centimeter is a metric unit of length equal to one hundredth of a meter.

Try: How many centimeters are in 2 meters?
MeasurementGrade 3GED

Circumference

Circumference is the distance around a circle.

Try: Which formula uses diameter to find circumference?
GeometryGrade 6GED

Coefficient

A coefficient is the number multiplied by a variable in a term.

Try: What is the coefficient of -9y?
AlgebraGrade 6GED

Composite Number

A composite number is a whole number greater than 1 that has more than two factors.

Try: Is 15 composite?
Number SystemGrade 4GED

Congruent Figures

Congruent figures have the same shape and the same size.

Try: Are two squares with side length 5 congruent?
GeometryGrade 7SAT

Constant

A constant is a fixed value that does not change.

Try: What is the constant in 2x + 11?
AlgebraGrade 6GED

Constant of Proportionality

The constant of proportionality is the constant ratio between two proportional quantities.

Try: In y = 6x, what is the constant of proportionality?
Ratios and ProportionsGrade 7GED

Coordinate Plane

The coordinate plane is a flat grid formed by a horizontal x-axis and vertical y-axis.

Try: What is the origin?
GeometryGrade 5GED

D

Decimal

A decimal is a number written with a decimal point to show parts of a whole.

Try: What fraction equals 0.25?
Number SystemGrade 4GED

Denominator

The denominator is the bottom number in a fraction.

Try: What is the denominator in 4/9?
Number SystemGrade 3GED

Dependent Variable

A dependent variable is the output value that changes based on the input.

Try: In C = 5n, if cost depends on number of tickets, which variable is dependent?
FunctionsGrade 6SAT

Diameter

The diameter is a line segment that passes through the center of a circle and touches both sides.

Try: If a circle has radius 7, what is its diameter?
GeometryGrade 6GED

Distributive Property

The distributive property multiplies a factor by each term inside parentheses.

Try: Expand 4(x + 3).
AlgebraGrade 6GED

Domain and Range

The domain is the set of possible inputs of a relation or function; the range is the set of possible outputs.

Try: For points (2, 7), (3, 7), (5, 9), what is the domain?
FunctionsGrade 8SAT

E

Elimination Method

The elimination method solves a system by adding or subtracting equations to remove a variable.

Try: In x + y = 7 and x – y = 3, what variable is eliminated if you add the equations?
AlgebraGrade 8GED

Equation

An equation is a statement that two expressions are equal.

Try: Is 4x + 7 an equation?
AlgebraGrade 6GED

Equivalent Fractions

Equivalent fractions are fractions that name the same value.

Try: Write a fraction equivalent to 2/3.
Number SystemGrade 3GED

Estimate

To estimate is to find an answer that is close enough, usually by rounding or using friendly numbers.

Try: Estimate 398 + 204 by rounding to the nearest hundred.
Problem SolvingGrade 3GED

Exponent

An exponent tells how many times to use a base as a factor.

Try: Evaluate 4^3.
AlgebraGrade 6GED

Expression

An expression is a number, variable, or combination of numbers and variables without an equal sign.

Try: Is 5n – 2 an expression?
AlgebraGrade 6GED

F

Factor

A factor is a number or expression that divides another number or expression evenly.

Try: Is 6 a factor of 24?
Number SystemGrade 4GED

Factoring

Factoring rewrites a number or expression as a product of factors.

Try: Factor 10x + 15.
AlgebraGrade 6GED

Formula

A formula is a rule written with symbols that shows how quantities are related.

Try: Which formula finds the area of a rectangle?
Problem SolvingGrade 5GED

Function

A function is a rule that gives exactly one output for each input.

Try: For f(x) = x + 4, what is f(6)?
FunctionsGrade 8SAT

G

Graph

A graph is a visual display of numbers, relationships, or data.

Try: On a coordinate graph, which axis is horizontal?
FunctionsGrade 5GED

Greatest Common Factor

The greatest common factor is the largest factor shared by two or more numbers.

Try: What is the GCF of 10 and 15?
Number SystemGrade 5GED

H

Histogram

A histogram uses bars to show how numerical data are grouped into intervals.

Try: Do bars in a histogram usually touch?
StatisticsGrade 6SAT

Hypotenuse

The hypotenuse is the longest side of a right triangle.

Try: A right triangle has side lengths 5, 12, and 13. Which side is the hypotenuse?
GeometryGrade 8GED

I

Improper Fraction

An improper fraction has a numerator that is greater than or equal to its denominator.

Try: Is 8/3 an improper fraction?
Number SystemGrade 4GED

Independent Variable

An independent variable is an input value that can be chosen or changed.

Try: In P = 2h, if pay depends on hours worked, which variable is independent?
FunctionsGrade 6SAT

Inequality

An inequality compares values using symbols such as <, >, <=, or >=.

Try: Solve 2x < 10.
AlgebraGrade 6GED

Input

An input is the value put into a function or rule.

Try: For f(x) = 2x, what is the output when the input is 4?
FunctionsGrade 6SAT

Integer

An integer is a whole number, its opposite, or zero.

Try: Which number is not an integer: -3, 0, 8, or 2.5?
Number SystemGrade 6GED

Irrational Number

An irrational number cannot be written as a fraction of two integers.

Try: Is sqrt(49) irrational?
Number SystemGrade 8SAT

J

Joint Frequency

Joint frequency is the number of data values that fit two categories at the same time.

Try: In a two-way table, where are joint frequencies usually found?
StatisticsGrade 8GED

K

Kilometer

A kilometer is a metric unit of length equal to 1,000 meters.

Try: How many meters are in 4 kilometers?
MeasurementGrade 4GED

L

Least Common Multiple

The least common multiple is the smallest positive multiple shared by two or more numbers.

Try: What is the LCM of 6 and 8?
Number SystemGrade 5GED

Like Terms

Like terms have the same variable parts raised to the same powers.

Try: Can 7x and 2x be combined?
AlgebraGrade 6GED

Line Plot

A line plot shows data values along a number line, often with marks above each value.

Try: What does each X usually represent on a line plot?
StatisticsGrade 3GED

Linear Equation

A linear equation is an equation whose graph is a straight line.

Try: Solve 3x + 2 = 14.
AlgebraGrade 7GED

M

Mathematical Model

A mathematical model represents a real situation using numbers, equations, diagrams, or graphs.

Try: What kind of model could show total cost for n tickets at $6 each?
Problem SolvingGrade 6GED

Mean

The mean is the sum of the values divided by the number of values.

Try: Find the mean of 6, 8, and 10.
StatisticsGrade 5GED

Median

The median is the middle value when data are listed in order.

Try: Find the median of 9, 3, 6.
StatisticsGrade 5GED

Meter

A meter is a metric unit of length equal to 100 centimeters.

Try: How many centimeters are in 3 meters?
MeasurementGrade 3GED

Mixed Number

A mixed number has a whole number and a fraction together.

Try: Convert 3 1/2 to an improper fraction.
Number SystemGrade 4GED

Mode

The mode is the value that appears most often in a data set.

Try: Find the mode of 4, 7, 7, 8, 9.
StatisticsGrade 5GED

Multiple

A multiple is the product of a number and a whole number.

Try: Is 28 a multiple of 7?
Number SystemGrade 4GED

N

Numerator

The numerator is the top number in a fraction.

Try: What is the numerator in 9/10?
Number SystemGrade 3GED

O

Opposite

The opposite of a number is the number the same distance from 0 on the other side of the number line.

Try: What is the opposite of -6?
Number SystemGrade 6GED

Order of Operations

The order of operations is the agreed order for simplifying expressions.

Try: Simplify 6 + 2 x 5.
AlgebraGrade 5GED

Ordered Pair

An ordered pair is two numbers written in order to locate a point on the coordinate plane.

Try: In the ordered pair (6, -1), what is the x-coordinate?
GeometryGrade 5GED

Outlier

An outlier is a data value that is far away from most of the other values.

Try: Which value looks like an outlier: 10, 11, 12, 13, 80?
StatisticsGrade 6GED

Output

An output is the value produced by a function or rule.

Try: For y = x + 5, what is the output when x = 8?
FunctionsGrade 6SAT

P

Parallel Lines

Parallel lines are lines in the same plane that never intersect.

Try: Do parallel lines intersect?
GeometryGrade 4GED

Percent

A percent is a number out of 100.

Try: What is 30% of 50?
Number SystemGrade 5GED

Percent Change

Percent change describes how much a value increases or decreases compared with the original value.

Try: A price rises from $40 to $50. What is the percent increase?
Ratios and ProportionsGrade 7GED

Perimeter

Perimeter is the total distance around a two-dimensional shape.

Try: What is the perimeter of a square with side length 6?
GeometryGrade 3GED

Perpendicular Lines

Perpendicular lines intersect to form right angles.

Try: What angle do perpendicular lines form?
GeometryGrade 4GED

Place Value

Place value is the value of a digit based on its position in a number.

Try: What is the value of 6 in 3,642?
Number SystemGrade 3GED

Polynomial

A polynomial is an expression made from constants, variables, and non-negative whole-number exponents using addition, subtraction, and multiplication.

Try: Is x^2 + 4x + 1 a polynomial?
AlgebraAlgebra 1SAT

Prime Number

A prime number is a whole number greater than 1 with exactly two factors: 1 and itself.

Try: Is 11 prime?
Number SystemGrade 4GED

Probability

Probability measures how likely an event is to happen.

Try: What is the probability of choosing a vowel from A, B, C, D, E?
StatisticsGrade 6GED

Proportion

A proportion is an equation that says two ratios are equal.

Try: Are 2/5 and 6/15 proportional?
Ratios and ProportionsGrade 6GED

Pythagorean Theorem

The Pythagorean theorem says that in a right triangle, a^2 + b^2 = c^2.

Try: A right triangle has legs 6 and 8. What is the hypotenuse?
GeometryGrade 8GED

Q

Quadratic Equation

A quadratic equation is an equation that can be written in the form ax^2 + bx + c = 0, where a is not 0.

Try: What values solve x^2 – 9 = 0?
AlgebraAlgebra 1SAT

R

Radius

The radius is a line segment from the center of a circle to any point on the circle.

Try: If a circle has diameter 18, what is its radius?
GeometryGrade 6GED

Range

The range of a data set is the difference between the greatest and least values.

Try: Find the range of 4, 10, 15.
StatisticsGrade 5GED

Ratio

A ratio compares two quantities by division.

Try: Write the ratio of 4 red marbles to 6 blue marbles.
Ratios and ProportionsGrade 6GED

Rational Number

A rational number is any number that can be written as a fraction of two integers.

Try: Is 0.75 rational?
Number SystemGrade 7GED

Reasonableness

Reasonableness is checking whether an answer makes sense for the problem.

Try: Why is 3.5 people not a reasonable answer for number of students?
Problem SolvingGrade 3GED

Rounding

Rounding replaces a number with a nearby number that is easier to use.

Try: Round 684 to the nearest hundred.
Number SystemGrade 3GED

S

Scale Factor

A scale factor is the number used to multiply side lengths when making a similar figure larger or smaller.

Try: A side length 5 is enlarged by scale factor 3. What is the new length?
Ratios and ProportionsGrade 7SAT

Scatter Plot

A scatter plot displays paired numerical data as points on a coordinate plane.

Try: If points rise from left to right, what kind of association is shown?
StatisticsGrade 8GED

Scientific Notation

Scientific notation writes a number as a value from 1 to less than 10 times a power of 10.

Try: Write 72,000 in scientific notation.
Number SystemGrade 8GED

Similar Figures

Similar figures have the same shape but not necessarily the same size.

Try: If a figure is enlarged by a scale factor of 3, is it similar to the original?
GeometryGrade 7SAT

Slope

Slope measures how steep a line is: the change in y divided by the change in x.

Try: What is the slope from (1, 2) to (4, 8)?
AlgebraGrade 8GED

Slope-Intercept Form

Slope-intercept form is the linear equation form y = mx + b.

Try: What is the slope of y = 4x – 7?
AlgebraGrade 8GED

Solution

A solution is a value that makes an equation or inequality true.

Try: Is x = 3 a solution of x + 5 = 8?
AlgebraGrade 6GED

Square Root

A square root of a number is a value that multiplies by itself to make that number.

Try: What is sqrt(144)?
Number SystemGrade 8GED

Substitution Method

The substitution method solves a system by replacing one variable with an equivalent expression.

Try: If y = x + 1 and x = 4, what is y?
AlgebraGrade 8GED

Surface Area

Surface area is the total area of all outside faces of a three-dimensional figure.

Try: Does surface area measure inside space or outside faces?
GeometryGrade 6GED

System of Equations

A system of equations is a set of equations solved together.

Try: If y = x + 2 and y = 6 when x = 4, does (4, 6) fit the first equation?
AlgebraGrade 8GED

T

Transformation

A transformation moves or changes a figure on the coordinate plane.

Try: Which transformation flips a figure over a line?
GeometryGrade 7SAT

Triangle

A triangle is a polygon with three sides and three angles.

Try: What is the sum of the angle measures in a triangle?
GeometryGrade 3GED

Two-Way Table

A two-way table organizes categorical data using rows and columns.

Try: Where are joint frequencies usually found in a two-way table?
StatisticsGrade 8GED

U

Unit Price

A unit price is the cost for one item or one unit.

Try: What is the unit price for 5 pens costing $10?
Ratios and ProportionsGrade 6GED

Unit Rate

A unit rate compares a quantity to one unit of another quantity.

Try: What is the unit rate for 24 miles in 3 hours?
Ratios and ProportionsGrade 6GED

V

Variable

A variable is a letter or symbol that represents a number or value.

Try: In 3n + 2, what is the variable?
AlgebraGrade 6GED

Vertex

A vertex is a corner point where two or more lines, rays, or sides meet.

Try: How many vertices does a triangle have?
GeometryGrade 4SAT

Volume

Volume measures the amount of space inside a three-dimensional figure.

Try: Find the volume of a box with dimensions 3, 4, and 5.
GeometryGrade 5GED

W

Whole Number

A whole number is 0 or a positive counting number.

Try: Is 8.5 a whole number?
Number SystemGrade 3GED

Width

Width is the distance across a shape or object from side to side.

Try: A rectangle has area 40 and length 10. What is its width?
MeasurementGrade 3GED

Word Problem

A word problem describes a math situation using words instead of only symbols.

Try: What should you identify first in a word problem?
Problem SolvingGrade 3GED

X

X-Axis

The x-axis is the horizontal number line on the coordinate plane.

Try: What is the y-coordinate of any point on the x-axis?
GeometryGrade 5GED

Y

Y-Intercept

The y-intercept is the point where a graph crosses the y-axis.

Try: What is the y-intercept of y = -3x + 8?
AlgebraGrade 8GED

Z

Zero

Zero is the number that represents none or no quantity.

Try: What is 12 + 0?
Number SystemGrade 3GED
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