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In mathematics, a unary operation is an operation with only one operand, i.e. a single input.[1] This is in contrast to binary operations, which use two operands.[2] An example is any function f : AA, where A is a set. The function f is a unary operation on A.

Common notations are prefix notation (e.g. ¬, ), postfix notation (e.g. factorial n!), functional notation (e.g. sinx or sin(x)), and superscripts (e.g. transpose AT). Other notations exist as well, for example, in the case of the square root, a horizontal bar extending the square root sign over the argument can indicate the extent of the argument.


Absolute value

Obtaining the absolute value of a number is a unary operation. This function is defined as [3] where is the absolute value of .


This is used to find the negative value of a single number. Here are some examples:


For any positive integer n, the product of the integers less than or equal to n is a unary operation called factorial. In the context of complex numbers, the gamma function is an unary operation extension of factorial.


In trigonometry, the trigonometric functions, such as , , and , can be seen as unary operations. This is because it is possible to provide only one term as input for these functions and retrieve a result. By contrast, binary operations, such as addition, require two different terms to compute a result.

Examples from programming languages


In JavaScript, these operators are unary:[4]

C family of languages

In the C family of languages, the following operators are unary:[5][6]

Unix shell (Bash)

In the Unix/Linux shell (bash/sh), '$' is a unary operator when used for parameter expansion, replacing the name of a variable by its (sometimes modified) value. For example:


See also


  1. ^ Weisstein, Eric W. "Unary Operation". Retrieved 2020-07-29.
  2. ^ Weisstein, Eric W. "Binary Operation". Retrieved 2020-07-29.
  3. ^ "Absolute value".
  4. ^ "Unary Operators".
  5. ^ "Chapter 5. Expressions and Operators". C/C++ Language Reference. Version 6.0. p. 109. Archived from the original on 2012-10-16. ((cite book)): |website= ignored (help)
  6. ^ "Unary Operators - C Tutorials - Sanfoundry".