identity function

noun

UK /aɪˈdɛntɪti ˈfʌŋkʃən/

US /aɪˈdɛntəti ˈfʌŋkʃən/

A rule that gives back the same number you put in.

The identity function turns 7 into 7 and 42 into 42.

SYNONYMS

identity map identity relation identity transformation unit function

RELATED WORDS

function domain codomain mapping mathematics

OTHER MEANINGS

2. In algebra, the function f(x) = x that leaves every element unchanged.

For the identity function, f(3) equals 3.

3. A function whose output is always exactly equal to its input.

The identity function is its own inverse.

4. In computing, a routine that simply returns the value it was given.

The identity function is often used as a default callback.