Integer Definition

An integer is a whole number from the set of negative, non-negative, and positive numbers. To be an integer, a number cannot be a decimal or a fraction. Here is a list of integers:

  • 130
  • -9
  • 0
  • 25
  • -7,685


Integers are all negative and positive whole numbers, and 0. Integers or integer values are part of various numbering systems.

Integer Definition And Examples

Numbering systems are ways of counting and categorizing real and imaginary objects. Integers are one set of numbers or numbering system you use every day.

Common numbering systems you may encounter include all these:

  • Real numbers
  • Natural numbers
  • Integers
  • Imaginary numbers
  • Rational numbers
  • Irrational numbers
  • Complex numbers
Avoid confusing the different groups of numbers with the different ways we represent them.

We usually write our numbers using Arabic numerals: 0, 1, 2, 3. But we can also represent them using Roman numerals (except for 0): I, II, III.

Set Of Integers

Mathematicians show sets of numbers using these brackets {}, and ellipsis … to show that the numbers continue without end. So we could show a set of integers like this:

... -4, -3, -2, -1,  0,  1,  2,  3,  4 ...

We understand that the negative numbers keep going, and so do the positive whole numbers.

Set Of Integers

Here are two different sets of numbers:

  1. What does this set mean? 1, 2, 3, 4, 5 ...
  2. Answer – That is the set of all positive integers.

  3. How about this one? 0, 2, 4, 6, 8, 10 ...
  4. Answer – That is the set of all non-negative, even integers.

A set of integers is represented by the symbol Z. A set is written as Z = {...}.

Integers That Are Not Whole Numbers

Negative integers are not whole numbers. Whole numbers are all counting numbers and 0. A set of integers that are not whole numbers looks like this:

-100, -86, -7, -13, -23, -744

A negative number that is not a decimal or fraction is an integer, but not a whole number.

Integer Examples

Integers are positive whole numbers and their additive inverse, any non-negative whole number, and the number zero by itself. Here are examples of integers:

  • Negative Integers: -1, -2, -3, -4, -5 and so on, without end
  • Non-negative Integers: 0 and all positive whole numbers, like 6, 7, 8, 9, and so on
  • Positive Integers: 1, 2, 3, 4, 5, without end ...
  • Zero: 0 all by itself

Integers Examples

Non-Integers Examples

Non-integers are any number that is a decimal, fraction, or mixed unit. These are all not integers:

  • Decimals: 3.14; 0.428571428571; 1.414213562373095
  • Fractions: ½; ¾; ⅞; 1½; 9/3; 3/7
  • Mixed units: 7’ - 3½”

Non-Integers Examples

Where Do We Use Integers?

Integers pop up in most things you count each day:

  • Temperature: 45 °C, -20 °C,  76 °F,  273.16 K
  • Grades: 65%, 100%, 50%
  • Teams: 11 football players; 9 baseball players; four four-square players; six members of the Chess Club
  • Altitude: Commercial planes fly at 35,000 feet above sea level, and higher
  • Coins: You have three quarters and two dimes, so you have 95 cents

Where We Use Integers

Whenever you are counting real objects such as books, pencils, shoes, hats, friends, or the number of hairs on your head, you are counting with integers.

Also, every time you round a number to a whole value, you change it from a decimal, fraction or mixed unit to an integer:

  • 5' 6" becomes the integer 6'
  • 378 becomes the integer 4
  • 98.6 °F becomes the integer 99 °F
  • $1.97 becomes the integer $2
  • 364.75 miles becomes the integer 365 miles

Characteristics Of Integers

Testing to see if a number is an integer is as easy as asking two questions:

  1. Is it a whole number? – Integer!
  2. Is it the number 0? – Integer!
  3. Is it negative of a whole number? – Integer!
  4. Does it include multiple parts, such as 5' 6" or $1.97Not an integer!
Zero plays a vital role on the number line. Learn more about the integer zero.

Which of the following are integers?:

  1. One
  2. 3.14159265358979
  3. -15 °C
  4. 113
  5. 9' 612"
  6. -365
  7. IV (Roman numerals!)
  8. $17.76
  9. 516

Only #1, 3, 6, and 8 are integers. The other numbers are perfectly fine numbers, but they are decimals, fractions, and mixed units.

Which Of The Following Are Integers

What you learned:

After working your way through this lesson and video, you have learned:

  • The definition of whole numbers and how to find them.
  • Integers are one of the many types of number systems.
  • Integers can be arranged into sets of numbers.
  • Decimals, mixed units, and fractions are not integers.
Instructor: Malcolm M.
Malcolm has a Master's Degree in education and holds four teaching certificates. He has been a public school teacher for 27 years, including 15 years as a mathematics teacher.

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