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[ahy-duh m-poht-nt, id-uh m-] /ˈaɪ dəmˈpoʊt nt, ˈɪd əm-/ Mathematics
unchanged when multiplied by itself.
an idempotent element.
Origin of idempotent
1865-70; idem + potent1 Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2017.
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British Dictionary definitions for idempotent


/ˈaɪdəmˌpəʊtənt; ˈɪd-/
(maths) (of a matrix, transformation, etc) not changed in value following multiplication by itself
Word Origin
C20: from Latin idem same + potent1
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for idempotent

1870, from Latin idem "the same" + potentem "powerful" (see potent).

Online Etymology Dictionary, © 2010 Douglas Harper
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idempotent in Technology

1. A function f : D -> D is idempotent if
f (f x) = f x for all x in D.
I.e. repeated applications have the same effect as one. This can be extended to functions of more than one argument, e.g. Boolean & has x & x = x. Any value in the image of an idempotent function is a fixed point of the function.
2. This term can be used to describe C header files, which contain common definitions and declarations to be included by several source files. If a header file is ever included twice during the same compilation (perhaps due to nested #include files), compilation errors can result unless the header file has protected itself against multiple inclusion; a header file so protected is said to be idempotent.
3. The term can also be used to describe an initialisation subroutine that is arranged to perform some critical action exactly once, even if the routine is called several times.
[Jargon File]

The Free On-line Dictionary of Computing, © Denis Howe 2010
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