algorithm

Etymology

From Middle English algorisme, augrym, from Anglo-Norman algorisme, augrim, from Medieval Latin algorismus, from Arabic الخَوَارِزْمِيّ (al-ḵawārizmiyy), the nisba of Persian mathematician Muḥammad ibn Mūsā al-Khwārizmī and a toponymic name meaning "person from Chorasmia". The spelling change (-s- > -th-) was influenced by unrelated Ancient Greek ἀριθμός (arithmós) (whence English arithmo-) .

noun

1. (countable) A collection of ordered steps that solve a mathematical problem. A precise step-by-step plan for a computational procedure that possibly begins with an input value and yields an output value in a finite number of steps.
   Informally, an algorithm is any well-defined computational procedure that takes some value, or set of values, as input and produces some value, or set of values, as output. An algorithm is thus a sequence of computational steps that transform the input into the output. 1990, Cormen, Leiserson, and Rivest, Introduction to Algorithms: page 1. Cambridge, MA, The MIT Press, 1999 (23rd printing)
   Mark Zuckerberg: No, I need the algorithm you used to rank chess players. / Eduardo Saverin: Are you OK? / Mark Zuckerberg: We're ranking girls. 2010, Aaron Sorkin, The Social Network
   The use of algorithms in policing is one example of their increasing influence on our lives. And, as their ubiquity spreads, so too does the debate around whether we should allow ourselves to become so reliant on them – and who, if anyone, is policing their use. 2013-07-26, Leo Hickman, “How algorithms rule the world”, in The Guardian Weekly, volume 189, number 7, page 26
   (Glover began his acceptance speech by saying, “First, I want to thank the algorithm that put us all here.”) 2018-02-26, Tad Friend, quoting Donald Glover, “Donald Glover Can’t Save You”, in The New Yorker
   It’s a computer – an algorithm – and if you’ve been in Iran lately, they take you out of the system. 2018-06-25, Sam Jones, “Ex-Nato chief refused visa waiver to US because of Iran trips”, in The Guardian
2. (loosely, by extension) A flowchart illustrating a decision-making process for human users, especially health care professionals.
3. 2023, Lee SG, Blood AJ, Cannon CP, Gordon WJ, Nichols H, Zelle D, Scirica BM, Fisher NDL, “Remote cardiovascular hypertension program enhanced blood pressure control during the COVID-19 pandemic”, in J Am Heart Assoc, volume 12, number 6, →DOI, →PMID, page e027296:
4. (uncountable, obsolete) Calculation with Arabic numerals; algorism.
5. (informal, social media, by extension) The algorithm used by social media websites to determine the contents of one's feed.