Math Glossary

Vocabulary is a key piece of math understanding! Use the glossary below to review or learn math terms used in 3rd grade.

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Angle When two line segments or rays share an endpoint and one rotates or turns away from the other, it forms an angle. The angle is named and measured by the amount of the turn or rotation.

Area The area of a flat, closed figure is a measure of the number of same-size squares that fill the shape with no spaces or overlaps. 

Associative Property When there are three or more addends, the sum will be the same no matter which way the addends are grouped.

Commutative Property For two addends in addition, changing the order of the addends does not change the sum. For two factors in multiplication, changing the order of the factors does not change the product.

Denominator The number below the fraction bar in a fraction that shows the number of equal-sized parts the whole has been divided into.

Distributive Property A number multiplied by two addends is the sum of the product of each addend and the number.

Equation A mathematical sentence with an equal sign that shows that two expressions have equal values. There are different kinds of equations.

Equivalent Fractions Fractions that are equal in value but may have different numerators and denominators. Note: When two fractions are equivalent, the numerator and denominator have the same relationship and represent the same part of a whole. Equivalent fractions represent the same location on a number line.

Estimate A value that represents about how much something is. Example. You can estimate the sum of two numbers by rounding. 

Expression A mathematical statement that represents a number of quantity. Expressions may include numbers, variables, and operators. An expressions does not include an equal symbol.

Fraction A number that is expressed in the form a/b where b does not equal 0. Fractions name a part of a whole or part of a set. The top number (numerator) is the number of parts taken or being considered; the bottom number (denominator) tells the number of equal parts in one whole. On a number line, a fraction with a numerator less than the denominator lies between 0 and 1.

Greater Than More than or bigger.  The symbol > means greater than.

Less Than Smaller than or not as big. The symbol < means less than.

Line Plot A graph that shows the spread of data along a number line using Xs (or dots) above a number to represent a data set. The Xs show the number of times the value occurs in that data set.

Numerator The integer above the line, or fraction bar, that shows how many parts are being considered out of the number of equal-sized parts indicated by the denominator. It is also the number to be divided by the denominator. For 2/3, the numerator 2 is divided by the denominator 3.

Operation An act upon two numbers to produce a number. The four basic operations of arithmetic are addition, subtraction, multiplication and division. The resulting numbers produced are called sum, difference, product and quotient. These are binary operations because they involve adding, subtracting, multiplying or dividing only two numbers at a time.

Order of Operations The order of operations is a set of rules for simplifying an expression with more than one operation. First, simplify any operations in parentheses. Second, simplify exponents. Third, simplify multiplication and division from left to right. Fourth, simplify addition and subtraction from left to right.

Perimeter The sum of the lengths of all of the sides of a polygon. The sides are measured in linear units such as feet, yards, or meters.

Place Value The place value of a digit is the value of the digit based on its position in the number. In the base-ten numeration system, the digit 2 in 526 is in the tens place and has a value of 20.

Total The sum of two or more numbers or the product of two or more numbers

Unit Fraction A unit fraction is a fraction with a numerator of 1. It represents one part of the total number of equal parts of a whole. Examples: 1/4, 1/2, and 1/3 are all unit fractions.