# Natural numbers and integers

Now that we have covered the names of numbers and the most popular systems of numerals, *let's start talking about Mathematics*. The first topic will be *natural numbers and integers*. What are they? Well, natural numbers are the ones you use to count, and integers include those which also show debt.

Let's elaborate:

Imagine someone just gave you a closed bag. One of the first things we want to know is what this bag contains. We are all curious, after all.

In mathematics, we call this bag of things *a set*; and there are two possibilities: the bag either does not contain anything, or it contains one or more things.

If there are things there, we will count them to know how many. *The numbers we use to count are the natural numbers.* They start with zero, and they go on as much as necessary.

Now let's imagine another situation. Imagine a friend of yours needs some eggs. The shops are too far to go get them there, so he knocks on your door to ask you for some. It is ok to lend him some eggs, but it is pretty obvious he will not be able to give them back to you. On a future occasion, he will need to go buy some eggs to be able to give you back the ones you lent him. This creates the concept of a debt.

In mathematics, *debt is represented with negative numbers*, and we indicate that with *a minus sign (-)*. So, in our previous example, if you lend your friend six eggs, now he will have minus six eggs. This is because we are considering that the first six eggs he buys will be to pay you back the ones you lent him.

Thus, we have:

*negative numbers – zero – positive numbers*

Positive numbers alone are called natural numbers, and together with the negative numbers, they are called integers.

In the next article, we will talk about what we can do with them.

*Learn + Mathematics*