un·ion 
(ynyən)
(ynyən)n.
1.
a. The act of uniting or the state of being united.
b. A combination so formed, especially an alliance or confederation of people, parties, or political entities for mutual interest or benefit.
2. Mathematics A set, every member of which is an element of one or another of two or more given sets.
3. Agreement or harmony resulting from the uniting of individuals; concord.
4.
a. The state of matrimony; marriage: "The element that was to make possible such a union was trust in each other's love" (Kate Chopin).
b. Sexual intercourse.
5.
a. A combination of parishes for joint administration of relief for the poor in Great Britain.
b. A workhouse maintained by such a union.
6. A labor union.
7. A coupling device for connecting parts, such as pipes or rods.
8. A device on a flag or ensign, occupying the upper inner corner or the entire field, that signifies the union of two or more sovereignties.
9. often Union
a. An organization at a college or university that provides facilities for recreation; a student union.
b. A building housing such facilities.
10. Union The United States of America regarded as a national unit, especially during the Civil War.
adj.
1. Union Of, relating to, or loyal to the United States of America during the Civil War: a Union soldier.
2. Of or relating to a labor union or labor union organizing: the union movement; union negotiations.
[Middle English, from Old French, from Late Latin ūniō, ūniōn-, from Latin ūnus, one; see oi-no- in the Appendix of Indo-European roots.]