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There are different sorts of numbers. This page is about the simplest ones.

They are called "natural numbers", or "counting numbers".

For other sorts of numbers, follow the links to
integers (whole numbers), rational numbers (fractions), real numbers, or complex numbers.

Look at the picture below. Is there a saucer for every cup? Is there a spoon for every cup and saucer?

Natural numbers 1-1 correspondence

When you have two sets of things that can be matched up, one-to-one, like the cups and the saucers, we say that the two sets have the same number of things. When we have sets that do not match up, like the cups and the spoons, they have different numbers of things.

The interesting thing is that we do not have to count. All we do is to see if they match up or not.

Arithmetic symbols.svg Mathematics Portal — All articles about mathematics.