Etymology From Middle English unyoun, from Old French union, from Late Latin ūniō, ūniōnem (“oneness, unity”), from Latin ūnus (“one”). Doublet of unio.
The act of uniting or joining two or more things into one.
2
The state of being united or joined; a state of unity or harmony.
3
Something united, or made one; something formed by a combination or coalition of parts or members; a confederation; a consolidated body; a league.
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A trade union; a workers' union.
In the autumn there was a row at some cement works about the unskilled labour men. A union had just been started for them and all but a few joined. One of these blacklegs was laid for by a picket and knocked out of time.1918, W[illiam] B[abington] Maxwell, chapter XXII, in The Mirror and the Lamp, Indianapolis, Ind.: The Bobbs-Merrill Company, →OCLC:
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An association of students at a university for social and/or political purposes; also in some cases a debating body.
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A joint or other connection uniting parts of machinery, such as pipes.
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Mathematics, Sciences, Set theory The set containing all of the elements of two or more sets.
Computing, Engineering, Mathematics, Natural sciences, Physical sciences, Programming, Sciences A data structure that can store any of various types of item, but only one at a time.
Unions are useful in those cases where you need to keep track of a value that can be represented as different data types during the lifetime of the program.2008, Kris Bell, Lars Ivar Igesund, Sean Kelly, Learn to Tango with D, page 58:
Nonius the senator hath a purple coat as stiff with jewels as his mind is full of vices; rings on his fingers worth 20,000 sesterces, and[…]an union in his ear worth an hundred pounds' weight of gold […]1624, Democritus Junior [pseudonym; Robert Burton], The Anatomy of Melancholy: […], 2nd edition, Oxford, Oxfordshire: […] John Lichfield and James Short, for Henry Cripps, →OCLC, partition II, section 3, member 3:
And in the cup an union shall he throw, Richer than that which four successive kings In Denmark's crown have worn.c. 1599–1602 (date written), William Shakespeare, “The Tragedie of Hamlet, Prince of Denmarke”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, →OCLC, [Act V, scene ii]:
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Historical An affiliation of several parishes for joint support and management of their poor; also the jointly-owned workhouse.
Etymology From Middle English unyoun, from Old French union, from Late Latin ūniō, ūniōnem (“oneness, unity”), from Latin ūnus (“one”). Doublet of unio.
Etymology From Middle English unyoun, from Old French union, from Late Latin ūniō, ūniōnem (“oneness, unity”), from Latin ūnus (“one”). Doublet of unio.
1
Belonging to, represented by, or otherwise pertaining to a labour union.