The empty set is a mathematical concept in set theory. It is defined as the set that contains no elements. In other words, an empty set is simply a set with no elements.

Here's a simple example of how you might define an empty set:

1. Define the set of all possible numbers.
2. For each number in this set, remove it from the set.
3. The result is an empty set.

In Python, you can create an empty set using the set() function:

empty_set = set()

This code creates an empty set called empty_set.