WordReference Random House Unabridged Dictionary of American English © 2026
set′ the′ory, 
  1. Mathematicsthe branch of mathematics that deals with relations between sets.
  • 1940–45

Collins Concise English Dictionary © HarperCollins Publishers::
set theory n
  1. the branch of mathematics concerned with the properties and interrelationships of sets
'set theory' also found in these entries (note: many are not synonyms or translations):
new maths - axiom of choice - continuum hypothesis - De Morgan's laws - new math - principle of mathematical induction - Russell's paradox - well-ordering theorem - Zorn's lemma - Schröder-Bernstein theorem

Forum discussions with the word(s) "set theory" in the title:


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