Math Glossary
Essential math terms and definitions for K-5 students
120 terms
A
Addition
Addition is the operation of combining two or more numbers to find their total. The result is called the sum.
Addend
An addend is any number that is being added to another number. In an addition problem, the numbers being added are called addends.
Associative Property
The associative property says that when you add or multiply three or more numbers, you can group them in any way and still get the same answer.
Angle
An angle is formed when two rays share a common endpoint called the vertex. Angles are measured in degrees.
Acute Angle
An acute angle is an angle that measures less than 90 degrees. It is smaller and sharper than a right angle.
Area
Area is the amount of space inside a flat shape. It is measured in square units, such as square centimeters or square inches.
B
Borrowing
Borrowing is the process of taking value from the next higher place-value column during subtraction when the top digit is smaller than the bottom digit.
Benchmark Fraction
A benchmark fraction is a common fraction that is easy to visualize and use as a reference point, such as 1/4, 1/2, or 3/4.
Bar Graph
A bar graph uses rectangular bars of different lengths or heights to show and compare data. The taller or longer the bar, the greater the value.
C
Cardinal Number
A cardinal number tells how many of something there are. It is used for counting, not for ordering.
Compare
To compare means to look at two or more numbers to see which is greater, which is less, or if they are equal.
Carrying
Carrying is the process of moving a value to the next place-value column during addition when the sum of a column is 10 or more.
Commutative Property
The commutative property says you can add or multiply numbers in any order and still get the same answer. It does not work for subtraction or division.
Common Denominator
A common denominator is a shared denominator that two or more fractions can use. It is needed when adding or subtracting fractions with different denominators.
Circle
A circle is a round shape where every point on the edge is the same distance from the center. That distance is called the radius.
Capacity
Capacity is the amount of liquid a container can hold. It is measured in units like liters, milliliters, cups, pints, quarts, and gallons.
Centimeter
A centimeter is a metric unit of length. There are 100 centimeters in 1 meter. It is used to measure small objects.
Coordinate Plane
A coordinate plane is a flat surface formed by two number lines that cross at right angles. The horizontal line is the x-axis and the vertical line is the y-axis.
D
Digit
A digit is any of the symbols 0, 1, 2, 3, 4, 5, 6, 7, 8, or 9 used to write numbers. Every number is made up of one or more digits.
Difference
The difference is the answer you get when you subtract one number from another. It tells how far apart two numbers are.
Division
Division is the operation of splitting a number into equal groups. It is the opposite of multiplication.
Dividend
The dividend is the number that is being divided in a division problem. It is the total amount you start with.
Divisor
The divisor is the number you divide by in a division problem. It tells you how many equal groups to make.
Distributive Property
The distributive property says that multiplying a number by a group of numbers added together is the same as doing each multiplication separately and then adding the results.
Denominator
The denominator is the bottom number in a fraction. It tells how many equal parts the whole is divided into.
Decimal
A decimal is a way of writing numbers that are not whole, using a decimal point to separate the whole part from the fractional part.
Decimal Point
A decimal point is the dot placed between the whole-number part and the fractional part of a decimal number. It separates ones from tenths.
Data
Data is a collection of facts, numbers, or information gathered through observation, measurement, or surveys. Data can be displayed in graphs, charts, and tables.
E
Even Number
An even number is a whole number that can be divided evenly into two equal groups with nothing left over. Even numbers end in 0, 2, 4, 6, or 8.
Equal
Equal means two values are exactly the same. The symbol = is placed between two things that have the same value.
Equivalent Fraction
Equivalent fractions are different fractions that represent the same value. You can create them by multiplying or dividing both the numerator and denominator by the same number.
Elapsed Time
Elapsed time is the amount of time that has passed between a start time and an end time.
Expression
An expression is a combination of numbers, variables, and operations (like +, -, x, /) that represents a value. Unlike an equation, an expression does not have an equals sign.
Equation
An equation is a math sentence that uses an equals sign (=) to show that two expressions have the same value.
F
Factor
A factor is a number that you multiply with another number to get a product. Factors divide evenly into a number with no remainder.
Fraction
A fraction is a number that represents a part of a whole. It is written as one number over another, separated by a line, like 1/2.
Foot
A foot is a customary unit of length equal to 12 inches. The plural is feet. It is used to measure medium-sized objects and heights.
Fact Family
A fact family is a group of related math facts that use the same set of numbers. Addition and subtraction form one type, and multiplication and division form another.
G
Greater Than
Greater than means one number has a larger value than another. The symbol > points toward the smaller number.
Greatest Common Factor
The greatest common factor (GCF) is the largest number that divides evenly into two or more numbers. It is used to simplify fractions.
H
Hundreds
The hundreds place is the third position from the right in a whole number. One hundred equals 10 groups of ten or 100 ones.
Hundredths
Hundredths is the second place to the right of the decimal point. One hundredth is one of one hundred equal parts, written as 0.01 or 1/100.
Height
Height is the measurement of how tall something is from bottom to top. It measures the vertical distance.
I
Integer
An integer is any whole number, including positive numbers, negative numbers, and zero. Integers do not include fractions or decimals.
Inverse Operation
An inverse operation is an operation that reverses or undoes another operation. Addition and subtraction are inverse operations, and so are multiplication and division.
Improper Fraction
An improper fraction is a fraction where the numerator is equal to or greater than the denominator. An improper fraction is equal to or greater than 1.
Inch
An inch is a customary unit of length. There are 12 inches in 1 foot. It is used to measure small objects.
Input-Output
An input-output table shows the relationship between two sets of numbers using a rule. You put a number in (input), apply the rule, and get a number out (output).
L
Less Than
Less than means one number has a smaller value than another. The symbol < points toward the smaller number.
Least Common Denominator
The least common denominator (LCD) is the smallest number that is a common denominator of two or more fractions. It is the least common multiple of the denominators.
Line
A line is a straight path that extends forever in both directions. It has no endpoints and is usually drawn with arrows on both ends.
Line Segment
A line segment is a part of a line that has two endpoints. Unlike a line, it does not go on forever.
Length
Length is the measurement of how long something is from one end to the other. It is measured in units like inches, feet, centimeters, or meters.
Line Graph
A line graph uses points connected by lines to show how data changes over time. It is great for showing trends and patterns.
M
Minuend
The minuend is the first number in a subtraction problem. It is the number you start with before taking something away.
Multiplication
Multiplication is a quick way of adding the same number over and over. It combines equal groups to find the total.
Mental Math
Mental math is the practice of doing calculations in your head without using paper, a pencil, or a calculator.
Mixed Number
A mixed number combines a whole number and a proper fraction. It shows a value that is more than one whole but not a complete next whole.
Meter
A meter is a metric unit of length equal to 100 centimeters or 1,000 millimeters. It is used to measure medium-sized lengths.
Mile
A mile is a customary unit of length equal to 5,280 feet or 1,760 yards. It is used to measure long distances.
Mean
The mean is the average of a set of numbers. To find the mean, add all the numbers together and divide by how many numbers there are.
Median
The median is the middle number in a set of data when the numbers are arranged in order from least to greatest. If there are two middle numbers, the median is their average.
Mode
The mode is the number that appears most often in a set of data. A data set can have one mode, more than one mode, or no mode at all.
N
Number
A number is a value that tells how many or how much of something there is. Numbers can be used for counting, measuring, and labeling.
Number Line
A number line is a straight line with numbers placed at equal intervals along its length. It helps us see the order and spacing of numbers.
Numerator
The numerator is the top number in a fraction. It tells how many parts you have out of the whole.
O
Ones
The ones place is the rightmost position in a whole number. It tells how many single units there are.
Odd Number
An odd number is a whole number that cannot be divided evenly into two equal groups. Odd numbers end in 1, 3, 5, 7, or 9.
Ordinal Number
An ordinal number tells the position or order of something in a list, such as first, second, or third.
Order of Operations
The order of operations is a set of rules that tells you the correct sequence to solve a math expression: Parentheses, Exponents, Multiplication and Division (left to right), Addition and Subtraction (left to right).
Obtuse Angle
An obtuse angle is an angle that measures more than 90 degrees but less than 180 degrees. It is wider and more open than a right angle.
Ordered Pair
An ordered pair is a pair of numbers written in parentheses (x, y) that describes a point on a coordinate plane. The first number is the x-coordinate and the second is the y-coordinate.
P
Place Value
Place value is the value of a digit based on its position in a number. Each place in a number is worth 10 times more than the place to its right.
Product
The product is the answer you get when you multiply two or more numbers together.
Parentheses
Parentheses are the symbols ( ) used in math to group parts of an expression together. Whatever is inside parentheses should be calculated first.
Proper Fraction
A proper fraction is a fraction where the numerator is smaller than the denominator. A proper fraction is always less than 1.
Percent
Percent means "per hundred" and is written with the % symbol. It expresses a number as a fraction of 100.
Proportion
A proportion is a statement that two ratios are equal. It shows that two comparisons represent the same relationship.
Point
A point is an exact location in space. It has no size, width, or length and is usually represented by a dot and labeled with a capital letter.
Perimeter
The perimeter is the total distance around the outside of a shape. You find it by adding up the lengths of all the sides.
Polygon
A polygon is a closed flat shape with three or more straight sides. Triangles, rectangles, and hexagons are all examples of polygons.
Parallel Lines
Parallel lines are two lines that are always the same distance apart and never cross or touch, no matter how far they extend.
Perpendicular Lines
Perpendicular lines are two lines that meet at a right angle (90 degrees), forming a square corner where they cross.
Pie Chart
A pie chart is a circular graph divided into slices to show how a whole is split into parts. Each slice represents a fraction or percentage of the total.
Pictograph
A pictograph uses pictures or symbols to represent data. Each picture stands for a certain number of items, shown in a key.
Probability
Probability is the chance that a particular event will happen. It is expressed as a number between 0 (impossible) and 1 (certain), or as a fraction or percent.
Pattern
A pattern is a sequence that follows a rule or repeats in a predictable way. Patterns can use numbers, shapes, or colors.
Q
R
Rounding
Rounding means replacing a number with a nearby number that is simpler or easier to work with. You round up if the digit is 5 or more, and round down if it is 4 or less.
Remainder
The remainder is the amount left over when a number cannot be divided evenly. It is always less than the divisor.
Regrouping
Regrouping is the process of rearranging numbers by place value when adding or subtracting. You trade between ones, tens, hundreds, and so on.
Ratio
A ratio compares two quantities by showing how much of one thing there is compared to another. It can be written as 3:2, 3 to 2, or 3/2.
Ray
A ray is a part of a line that starts at one point (the endpoint) and extends forever in one direction.
Right Angle
A right angle is an angle that measures exactly 90 degrees. It looks like a perfect square corner.
Rectangle
A rectangle is a quadrilateral with four right angles (90-degree corners). Opposite sides of a rectangle are equal in length and parallel.
S
Sum
The sum is the answer you get when you add two or more numbers together.
Subtraction
Subtraction is the operation of taking one number away from another to find the difference. It is the opposite of addition.
Subtrahend
The subtrahend is the number being subtracted in a subtraction problem. It is the amount you take away.
Simplify
To simplify a fraction means to reduce it to its smallest equivalent form by dividing both the numerator and denominator by their greatest common factor.
Square
A square is a special rectangle where all four sides are the same length and all four angles are right angles (90 degrees).
Symmetry
A shape has symmetry if it can be divided into two halves that are mirror images of each other. The dividing line is called the line of symmetry.
Sequence
A sequence is an ordered list of numbers or objects that follow a specific pattern or rule.
Skip Counting
Skip counting is counting forward or backward by a number other than 1. It is a useful way to learn multiplication and see number patterns.
T
Tens
The tens place is the second position from the right in a whole number. Each group of ten ones makes one ten.
Thousands
The thousands place is the fourth position from the right in a whole number. One thousand equals 10 groups of one hundred or 1,000 ones.
Tenths
Tenths is the first place to the right of the decimal point. One tenth is one of ten equal parts, written as 0.1 or 1/10.
Triangle
A triangle is a polygon with exactly three sides, three vertices, and three angles. The sum of all three angles in a triangle is always 180 degrees.
Table
A table organizes data into rows and columns so it is easy to read and compare. Tables are one of the simplest ways to display information.
U
Unit Fraction
A unit fraction is a fraction with 1 as the numerator. It represents one equal part of a whole.
Unit Conversion
Unit conversion is the process of changing a measurement from one unit to another, such as converting inches to centimeters or pounds to kilograms.
V
Vertex
A vertex is a point where two sides of a shape meet to form an angle. The plural of vertex is vertices.
Volume
Volume is the amount of space a three-dimensional object takes up. It is measured in cubic units such as cubic centimeters or cubic inches.
Variable
A variable is a letter or symbol that stands for an unknown number. Common variables include x, y, and n.
W
Whole Number
A whole number is any of the counting numbers along with zero: 0, 1, 2, 3, 4, and so on. Whole numbers have no fractions or decimals.
Width
Width is the measurement of how wide something is from side to side. It is the shorter dimension of a rectangle.
Weight
Weight is a measurement of how heavy something is. Common units include pounds, ounces, grams, and kilograms.