union

1 of 2

noun

ˈyün-yən 

plural unions

1

a

: an act or instance of uniting or joining two or more things into one: such as

(1)

: the formation of a single political unit from two or more separate and independent units

(2)

: a uniting in marriage

also : sexual intercourse

(3)

: the growing together of severed parts

b

: a unified condition : combination, junction

a gracious union of excellence and strength

2

: something that is made one : something formed by a combining or coalition of parts or members: such as

a

: a confederation of independent individuals (such as nations or persons) for some common purpose

b(1)

: a political unit constituting an organic whole formed usually from units which were previously governed separately (such as England and Scotland in 1707) and which have surrendered or delegated their principal powers to the government of the whole or to a newly created government (such as the U.S. in 1789)

(2)

the Union in U.S. history : the group of states that remained part of the United States after 11 southern states seceded in 1860 and 1861 and formed the Confederacy (see confederacy sense 2b) : the federal union of states during the period of the American Civil War

c

Union : an organization on a college or university campus providing recreational, social, cultural, and sometimes dining facilities

also : the building housing such an organization

d

: the set of all elements belonging to one or more of a given collection of two or more sets

called also join, sum

e

: labor union

3

a

: a device emblematic of the union of two or more sovereignties borne on a national flag typically in the upper inner corner or constituting the whole design of the flag

b

: the upper inner corner of a flag

4

: any of various devices for connecting parts (as of a machine)

especially : a coupling for pipes or pipes and fittings

union

2 of 2

adjective

: of, relating to, dealing with, or constituting a union

especially, Union : of, relating to, or being the side favoring the Union in the American Civil War

Union troops

Synonyms

Noun

• merger
• unification
• merging
• consolidation

Examples of union in a Sentence

Noun

She joined the teachers' union.

An embryo is created through the union of sperm and egg.

a perfect union of Eastern and Western music

Recent Examples on the Web

Noun

In addition, Woodard was a member of a players’ union, the United Basketball Players Association. —Michael McCann, Sportico.com, 7 July 2025

Staff employee unions at outlets including The New York Times and Politico have raised concerns about whether recent deals with AI companies violate employee contracts about AI use. —Marta Biino, semafor.com, 7 July 2025

Adjective

Infrastructure activity would bring thousands of good jobs to union and non-union workers. —Jamie Rubin, New York Daily News, 18 June 2025

Per sources, both union and non-union crew members were in favor of an IATSE contract. —Katie Campione, Deadline, 29 May 2025

Word History

Etymology

Noun

Middle English, from Anglo-French, from Late Latin union-, unio oneness, union, from Latin unus one — more at one

First Known Use

Noun

15th century, in the meaning defined at sense 1a

Adjective

1634, in the meaning defined above

Phrases Containing union

• anti-union
• civil union
• company union
• craft union
• credit union
• industrial union
• inter-union
• labor union
• personal union
• postal union
• student union
• trade union
• union card
• union church
• union jack
• union shop
• union suit
• union territory
• vertical union

Rhymes for union

• antiunion
• communion
• disunion
• nonunion

Kids Definition

union

1 of 2 noun

ˈyün-yən

1

a

: an act or instance of uniting two or more things into one

the union of Scotland and England

union of a man and woman in marriage

b

: combination sense 1

the union of science and technology to solve modern problems

2

a

: something (as a nation) formed by a combining of parts or members

b

: labor union

c

: the mathematical set that contains all of the elements which are included in at least one of two or more sets

the union of the set {1, 2, 3} and the set {3, 4, 5} is the set {1, 2, 3, 4, 5}

3

: a device for connecting parts (as pipes)

Union

2 of 2 adjective

: of, relating to, or being the side favoring the federal union in the American Civil War

the Union army

Medical Definition

union

noun

ˈyü-nyən 

: an act or instance of uniting or joining two or more things into one: as

a

: the growing together of severed parts

union of a fractured bone

b

: a chemical combination : bond

c

: the joining of two germ cells in the process of fertilization

Legal Definition

union

noun

1

: an act or instance of uniting or joining two or more things into one

especially : the formation of a single political unit from two or more separate and individual units

2

: something that is made one : something formed by a combining or coalition of its members: as

a

: a confederation of independent individuals (as nations or persons) for some common purpose

b

: a political unit constituting an organic whole formed usually from previously independent units (as England and Scotland in 1707) which have surrendered their principal powers to the government of the whole or to a newly created government (as the U.S. in 1789)

c

: labor union