Numbers are considered the heart of Mathematics, and rightly so because without numbers Maths would simply not exist.
The importance of numbers
If we think about it for a moment, numbers are everywhere in our daily lives, and they help us to think logically and to keep track of the things we do. For example, numbers help us with simple tasks like calculating the time that it takes you to get from home to your place of work, the amount of money that you need to pay for your shopping, and the amount of bags that you need to carry your shopping home, but they are also especially useful to solve more complex problems in the world of sciences and engineering, like calculating the amount of fuel that will be needed to get a rocket into space, or the number of lorries that a warehouse needs to transport their customer's orders safely and on time.
What are the different types of numbers?
Numbers can be classified into different groups according to the types of numbers that they include. Let's take a look.
Natural and whole numbers
Natural numbers are also known as counting numbers, because these are the numbers that you first learn how to count with. They include all positive numbers greater than zero. That is 1, 2, 3, 4, 5, 6, and so on.
They are represented with the letter N. The set notation for natural numbers is as follows:
N = {1, 2, 3, 4, 5, ...}
Whole numbers are closely related to natural numbers, with one main difference, as you can see from the definition below.
Whole numbers are basically the natural numbers plus zero. Whole numbers do not include negative numbers, fractions or decimals.
They are represented with the letter W, and their set notation is shown below:
W = {0, 1, 2, 3, 4, 5, ...}
All natural numbers are whole numbers, but not all whole numbers are natural numbers, this is the case for zero. Let's see this in a diagram.
Representation of natural and whole numbers, Marilú García De Taylor - StudySmarter Originals
Natural and whole numbers can be represented on the number line as follows:
Natural and whole numbers on the number line, Marilú García De Taylor - StudySmarter Originals
Please refer to Natural Numbers to learn more about this type of number.
Integers
Integers include all positive numbers, zero and negative numbers. Again, integers do not include fractions or decimals.
They are represented with the letter Z, and their set notation is as follows:
Z = {..., -4, -3, -2, -1, 0, 1, 2, 3, 4, ...}
If we expand the previous diagram to include integers, it will look like this:
Representation of integers, Marilú García De Taylor - StudySmarter Originals
Looking at the diagram above, we can say that not all integers are natural and whole numbers, but all natural and whole numbers are integers. On the number line, integers can be represented like this:
Integers on the number line, Marilú García De Taylor - StudySmarter Originals
Some examples of integer numbers are:
-45, -12, -1, 0, 35, and 946
Check out the Integers article for more details and examples.
Rational and irrational numbers
Rational numbers include all numbers that can be expressed as a fraction in the form 
, where p and q are integers and 
. This group of numbers includes fractions and decimals. Rational numbers are represented with the letter Q.
All integers, natural and whole numbers are rational numbers, as they can be expressed as a fraction with a denominator of 1. For example, 3 can be expressed as a fraction like this 
.
Representation of rational numbers. Marilú García De Taylor - StudySmarter Originals
Some examples of rational numbers are:
Irrational numbers are numbers that can't be expressed as a fraction of two integers. Irrational numbers have non-repeating decimals that never end, and have no pattern whatsoever. They are represented with the letter Q'.
Representation of irrational numbers, Marilú García De Taylor - StudySmarter Originals
Some examples of irrational numbers are:
There are numbers with non-terminating decimals that are actually rational. This is the case of numbers with non-terminating decimals that repeat in a pattern, as they can be expressed as a fraction of two integers. For example, 
the bar above the decimal 1 means that it repeats forever. So, 
is a rational number.
Real numbers
Real numbers include all the numbers that you can think of, which you can find in the real world, apart from imaginary numbers. Real numbers are represented with the letter R, and they include all rational and irrational numbers, therefore the set of real numbers can be represented as 
.
Representation of real numbers, Marilú García De Taylor - StudySmarter Originals
Some examples of real numbers are:
Check out the Real Numbers article to expand your knowledge about this topic.
Imaginary numbers
Imaginary numbers are the root of negative numbers.
We know that we can't take the square root of negative numbers, because there is no number that when squared will result in a negative number. In this case, we need to use imaginary numbers. To do this, we say that 
.
Types of Numbers - Key takeaways
- Real numbers are all the numbers that you can think of, apart from imaginary numbers.
- Real numbers include all rational and irrational numbers.
- Rational numbers can be expressed as a fraction of two integers, while irrational numbers can't.
- Integers include all negative and positive whole numbers.
- Whole numbers are all natural numbers plus zero.
- Natural numbers, also known as counting numbers, are all numbers starting from 1.
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can be written as 
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