Editing Union (set theory) (section)

== History and etymology ==
{{Further|History of set theory}}
The english word ''union'' comes from the term in [[middle French]] meaning "coming together", which comes from the [[Post-Classical Latin language|post-classical Latin]] ''unionem'', "oneness".<ref>{{Cite web |title=Etymology of "union" by etymonline |url=https://www.etymonline.com/word/union |access-date=2025-04-10 |website=etymonline |language=en-US}}</ref> The original term for union in set theory was ''Vereinigung'' (in german), which was introduced in 1895 by [[Georg Cantor]].<ref>{{Cite journal |last=Cantor |first=Georg |date=1895-11-01 |title=Beiträge zur Begründung der transfiniten Mengenlehre |url=https://link.springer.com/article/10.1007/BF02124929 |journal=Mathematische Annalen |language=de |volume=46 |issue=4 |pages=481–512 |doi=10.1007/BF02124929 |issn=1432-1807}}</ref> The english use of ''union'' of two sets in mathematics began to be used by at least 1912, used by [[James Pierpont (mathematician)|James Pierpont]].<ref>{{Cite book |last=Pierpont |first=James |url=https://archive.org/details/lecturesonthethe031634mbp/page/22/mode/2up?q=union |title=Lectures On The Theory Of Functions Of Real Variables Vol II |date=1912 |publisher=Ginn And Company |others=Osmania University, Digital Library Of India}}</ref><ref>''[[Oxford English Dictionary]]'', “union (''n.2''), sense III.17,” March 2025, https://doi.org/10.1093/OED/1665274057</ref> The symbol <math>\cup</math> used for union in mathematics was introduced by [[Giuseppe Peano]] in his ''[[Arithmetices principia, nova methodo exposita|Arithmetices principia]]'' in 1889, along with the notations for intersection <math>\cap</math>, set membership <math>\in</math>, and subsets <math>\subset</math>.<ref>{{Cite web |title=Earliest Uses of Symbols of Set Theory and Logic |url=https://mathshistory.st-andrews.ac.uk/Miller/mathsym/set/ |access-date=2025-04-10 |website=Maths History |language=en}}</ref>