Merriam-Webster Logo
  • Dictionary
  • Thesaurus
  • Medical
  • Scrabble
  • Spanish Central
  • Learner's Dictionary


noun \ˈyün-yən\

Simple Definition of union

  • : an organization of workers formed to protect the rights and interests of its members

  • : an act of joining two or more things together

  • : a group of states or nations that are ruled by one government or that agree to work together

Full Definition of union

  1. 1 a :  an act or instance of uniting or joining two or more things into one: 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. 2 :  something that is made one :  something formed by a combining or coalition of parts or members: as a :  a confederation of independent individuals (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 (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 (as the United States in 1789) (2) capitalized :  the federal union of states during the period of the American Civil War c capitalized :  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. 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. 4 :  any of various devices for connecting parts (as of a machine); especially :  a coupling for pipes or pipes and fittings

Examples of union

  1. She joined the teachers' union.

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

  3. a perfect union of Eastern and Western music

Origin of union

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

First Known Use: 15th century




Definition of union

  1. :  of, relating to, dealing with, or constituting a union; especially capitalized :  of, relating to, or being the side favoring the Union in the American Civil War <Union troops>


First Known Use of union


UNION Defined for Kids


noun \ˈyün-yən\

Definition of union

  1. 1 :  an act or instance of uniting or joining two or more things into one <The river is formed by the union of two tributaries.>

  2. 2 :  something (as a nation) formed by a combining of parts or members

  3. 3 cap :  the United States

  4. 4 cap :  the group of states that supported the United States government in the American Civil War

  5. 5 :  a device for connecting parts (as pipes)

  6. 6 :  labor union



Definition of Union

  1. :  relating to the group of states that supported the United States government in the American Civil War <Union soldiers>

Medical Dictionary


noun \ˈyü-nyən\

Medical Definition of union

  1. :  an act or instance of uniting or joining two or more things into one: asa:  the growing together of severed parts <union of a fractured bone>b:  a chemical combination :  bondc:  the joining of two germ cells in the process of fertilization

Seen and Heard

What made you want to look up union? Please tell us where you read or heard it (including the quote, if possible).


February 12, 2016

of, relating to, or suggestive of marble

Get Word of the Day daily email!


Take a 3-minute break and test your skills!


How much does a batman (the Turkish unit of measurement) weigh?

100 pounds 2.2 pounds 16.96 pounds 196.5 pounds
Name That Thing

10 quick questions: hear them, spell them, and see how your skills compare to the crowd.


Test Your Knowledge - and learn some interesting things along the way.