# Definition:Complement

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## Disambiguation

This page lists articles associated with the same title. If an internal link led you here, you may wish to change the link to point directly to the intended article.

**Complement** may refer to:

- Geometry:
- Complementary angles: two angles whose measures add up to the measure of a right angle.
- Complements of Parallelograms: The extra bits that need to be added to a pair of parallelograms sharing a line for their diagonals that need to be added to make one big parallelogram.

- Relation Theory:
- Complement of Relation: for a relation $\RR$, its
**complement**is all those pairs which are not in $\RR$.

- Complement of Relation: for a relation $\RR$, its

- Set Theory:
- Set Complement or Relative Complement: two related concepts: all the elements of a set which are not in a given subset.

- Logic:
- Logical Complement: In logic, the negation of a statement.

- Lattice Theory:
- Complement of Lattice Element: In a strong and precise sense, an incomparable element of an element of a bounded lattice.

- Graph Theory:
- Complement of Graph: a graph with the same vertex set but whose edge set is all those edges not in that graph.

## Linguistic Note

The word **complement** comes from the idea of **complete-ment**, it being the thing needed to **complete** something else.

It is a common mistake to confuse the words **complement** and **compliment**. Usually the latter is mistakenly used when the former is meant.