set theory

noun

: a branch of mathematics or of symbolic logic that deals with the nature and relations of sets
set theoretic adjective

Examples of set theory in a Sentence

Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
But the math of set theory, which so often dwells in a world beyond proof, tends to look more like physics or biology, as Aguilera put it. Gregory Barber, Quanta Magazine, 20 June 2025 But the viewer doesn’t need to know a thing about set theory to find her organization of lines and angles beautiful. Grace Edquist, Vogue, 25 Nov. 2024 An Alternative Mathematics Some experts were therefore determined to reject the axiom of choice and instead work only with the eight fundamental truths of Zermelo-Fraenkel set theory. Manon Bischoff, Scientific American, 1 Oct. 2024

Word History

First Known Use

1936, in the meaning defined above

Time Traveler
The first known use of set theory was in 1936

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Cite this Entry

“Set theory.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/set%20theory. Accessed 8 Sep. 2025.

Kids Definition

set theory

noun
: a branch of mathematics that deals with sets and with relations between sets
set-theoretic
-ˌthē-ə-ˈret-ik
adjective

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