In set theory, the **complement** of a set is the set of all elements that are not in .

## Absolute complement

If the universal set is defined, then, in terms of the relative complement, the complement of is

## Relative complement

Given two sets , the relative complement of in , denoted as (sometimes ) is

## Example

- Suppose the universe is the set of all letters in the English alphabet. The complement of the set of all vowels in , ( being the set), is the set of all consonants.

## See also

- Negation (equivalent in logic)
- Intersection (set theory)
- Union
- Symmetric difference