# Definition:Operation/Unary Operation

< Definition:Operation(Redirected from Definition:Unary)

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## Contents

## Definition

A **unary operation** is the special case of an operation where the operation has exactly one operand.

Thus, a **unary operation** on a set $S$ is a mapping whose domain and codomain are both $S$.

## Examples

### Square Root

An example of a **unary operation** from algebra is $\sqrt{}$ (that is, the square root sign).

### All Mappings are Unary

To a set theorist, all mappings are unary operations.

## Linguistic Note

The word **unary** is pronounced ** yoo-nary**.

Hence when the indefinite article precedes it, the form is (for example) ** a unary operation**.

## Sources

- 1965: Seth Warner:
*Modern Algebra*... (previous) ... (next): $\S 18$ - 1966: Richard A. Dean:
*Elements of Abstract Algebra*... (previous) ... (next): $\S 0.5$ - 1970: B. Hartley and T.O. Hawkes:
*Rings, Modules and Linear Algebra*... (previous) ... (next): $\S 1.1$: The definition of a ring - 1996: H. Jerome Keisler and Joel Robbin:
*Mathematical Logic and Computability*... (previous) ... (next): Appendix $\text{A}.8$: Cartesian Product