Math Glossary
Plain-English definitions for the terms that show up across grades 1–6 — organized by category, not forced into strict alphabetical order, so related ideas sit together.
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Numbers & Operations
Sum
The answer to an addition problem.
Example: The sum of 4 and 5 is 9.
Difference
The answer to a subtraction problem.
Example: The difference between 10 and 3 is 7.
Product
The answer to a multiplication problem.
Example: The product of 6 and 7 is 42.
Quotient
The answer to a division problem.
Example: The quotient of 20 ÷ 4 is 5.
Remainder
What's left over when a number doesn't divide evenly.
Example: 27 ÷ 6 = 4 remainder 3.
Factor
A number that divides evenly into another number.
Example: 3 and 4 are both factors of 12.
Multiple
The result of multiplying a number by a whole number.
Example: 12 is a multiple of 3 (3 × 4).
Prime Number
A number greater than 1 with exactly two factors: 1 and itself.
Example: 7 is prime — only 1 × 7 makes it.
Composite Number
A number with more than two factors.
Example: 8 is composite: 1, 2, 4, and 8 are all factors.
Place Value
The value of a digit based on its position in a number.
Example: In 3,482, the 4 is worth 400 (hundreds place).
Rounding
Adjusting a number to the nearest ten, hundred, or other friendly value.
Example: 47 rounds to 50 (nearest ten).
Estimate
A reasonably close answer found without exact calculation.
Example: An estimate of 29 × 61 is about 1,800 (30 × 60).
Fractions, Decimals & Percents
Numerator
The top number in a fraction — how many pieces you have.
Example: In 3/4, the numerator is 3.
Denominator
The bottom number in a fraction — how many equal pieces the whole is split into.
Example: In 3/4, the denominator is 4.
Equivalent Fractions
Different fractions that represent the same amount.
Example: 1/2 and 2/4 are equivalent.
Simplest Form
A fraction reduced so the numerator and denominator share no common factor.
Example: 4/8 simplified is 1/2.
Mixed Number
A whole number combined with a fraction.
Example: 2 1/2 means two whole ones plus a half.
Improper Fraction
A fraction where the numerator is bigger than the denominator.
Example: 5/2 is improper (it equals 2 1/2).
Decimal
A way of writing a fraction of ten, a hundred, etc. using a decimal point.
Example: 0.5 means 5/10, or one-half.
Percent
A fraction out of 100, shown with a % sign.
Example: 50% means 50 out of 100, or one-half.
Ratio
A comparison between two quantities.
Example: A ratio of 3 red to 2 blue marbles is written 3:2.
Rate
A ratio comparing two different kinds of units.
Example: 60 miles per hour is a rate.
Unit Rate
A rate simplified to "per one" unit.
Example: If 4 apples cost $2, the unit rate is $0.50 per apple.
Geometry & Measurement
Perimeter
The distance all the way around the outside edge of a shape.
Example: A 4×3 rectangle has a perimeter of 14.
Area
The amount of surface a flat shape covers, measured in square units.
Example: A 4×3 rectangle has an area of 12 square units.
Volume
The amount of space a 3D shape takes up, measured in cubic units.
Example: A 2×3×4 box has a volume of 24 cubic units.
Array
Objects arranged in equal rows and columns.
Example: 3 rows of 4 chairs form a 3×4 array (12 chairs).
Angle
The space between two lines that meet at a point, measured in degrees.
Example: A right angle measures exactly 90°.
Symmetry
When one half of a shape is a mirror image of the other half.
Example: A butterfly's wings show symmetry.
Coordinate Plane
A grid used to describe exact locations using two numbers (x, y).
Example: The point (3, 2) is 3 right and 2 up from the center.
Algebra & Data
Variable
A letter that stands in for an unknown number.
Example: In x + 5 = 9, x is a variable equal to 4.
Expression
A math phrase with numbers and operations, but no equals sign.
Example: 3x + 2 is an expression.
Equation
A math statement that says two things are equal.
Example: 3x + 2 = 11 is an equation.
Order of Operations
The agreed-upon order for solving expressions with multiple operations (parentheses, exponents, multiplication/division, addition/subtraction).
Example: 3 + 4 × 2 = 11, not 14.
Negative Number
A number less than zero.
Example: −5 is 5 less than 0, like being 5 degrees below freezing.
Mean (Average)
Add up all the values and divide by how many there are.
Example: The mean of 2, 4, 6 is (2+4+6)÷3 = 4.
Median
The middle value when a set of numbers is put in order.
Example: The median of 3, 5, 9 is 5.
Mode
The value that appears most often in a set of numbers.
Example: The mode of 2, 2, 5, 7 is 2.
Range
The difference between the largest and smallest values in a set.
Example: The range of 3, 8, 15 is 15 − 3 = 12.