Glossary of 5th Grade Mathematical Terms: Definitions and Examples

Knowing the proper vocabulary terms can boost your child's confidence level and willingness to participate in class discussions. It may also increase standardized test scores and his ability to correctly solve word problems. While reviewing this mathematical glossary, encourage your child to rephrase the definition in her own words. You may also create flash cards to review these terms daily.

Math Terms and Definitions for 5th Graders

Fractions

Common denominator

A common denominator is a multiple of the denominators of two or more fractions, so that the fractions can be more easily compared and worked with. For example, a common denominator for the fractions 3/10 and 4/5 is 20, since both 5 and 10 can be multiplied by another number to equal 20. The fraction 3/10 equals 6/20, while 4/5 equals 16/20.

Equivalent fractions

These are fractions that have an equal value. Examples of equivalent fractions would be 1/2 and 4/8.

Improper fraction

A fraction is termed an 'improper fraction' when its numerator is bigger than its denominator. These fractions can be changed to a mixed number. One example of an improper fraction would be 15/4.

Least common denominator (LCD)

This is the smallest number that can be a multiple of each denominator. The fractions 3/10 and 4/5 have a LCD of 10.

Mixed number

Mixed numbers occur when you change an improper fraction. These numbers include both a whole number and a fraction. The improper fraction 15/4 would be changed to the mixed number 3 3/4.

Number Relations

Composite number

A composite number is the opposite of a prime number. Composite numbers have more than two factors. An example is 16.

Divisor

This is the number on the outside of the division bracket (the symbol used in long division). Divisors are being divided into a number. In the problem 16 ÷ 4, four would be the divisor.

Exponent

An exponent is a shorthand way of indicating (in a superscript) how many times to multiply a number. It is represented by the ^ symbol. For example, 3^3 = 3 x 3 x 3 = 27.

Factors

Factors are numbers that are multiplied together to create a new number. For example, in 6 x 7 = 42, six and seven are both factors.

Multiple

A multiple is a number that can be divided into another number evenly, leaving no remainder. A multiple of six is 36.

Prime number

A prime number is a number that cannot be divided by any numbers other than one and itself. Examples of prime numbers include 5, 17 and 29.

Geometry

Vertex

An angle's vertex is the point where two rays, lines or line segments meet. For example, line segment AB meets line segment BD and forms angle ABD. The point where they meet, B, is the vertex.

Protractor

A protractor is a tool, usually shaped like a half circle, that measures angles. A protractor has a movable arm that helps you get accurate angle measurements.

Parallel lines

Lines that run an alongside one another without ever crossing are parallel lines. Parallel lines remain the same distance apart from top to bottom. These lines are represented using a symbol that looks like this: II.

Perpendicular lines

Perpendicular lines are lines that cross each other forming a right angle, which measures 90 degrees. Perpendicular lines are represented using an upside down T.