ELI5: Explain Like I'm 5

Partition (number theory)

A partition in number theory is like having a bunch of cookies and figuring out how many different ways you can divide them up into groups. For example, if you have three cookies, you could divide them up into three groups of one, or two groups of one and one group of two, or one group of three. Each of these ways of dividing up the cookies is known as a partition.

In number theory, instead of dividing up cookies, we're dividing up numbers. Specifically, we're looking at how many different ways a certain number can be expressed as the sum of smaller numbers. For example, the number 4 can be partitioned in the following ways:

- 4
- 3 + 1
- 2 + 2
- 2 + 1 + 1
- 1 + 1 + 1 + 1

So, 4 has five different partitions.

Partitions are interesting in number theory because they show up in lots of different areas, like algebra, geometry, and even physics. Mathematicians have been studying partitions for hundreds of years, and there are still many mysteries about them that we don't understand!