noun: 1. the act of allying or state of being allied. 2. a formal agreement or treaty between two or more nations to cooperate for specific purposes. 3. a merging of efforts or interests by persons, families, states, or organizations: an alliance between church and state. 4. the persons or entities so allied. 5. marriage or the relationship created by marriage between the families of the spouses. 6. correspondence in basic characteristics; affinity: the alliance between logic and metaphysics. 7. the act of allying or state of being allied; union; confederation. 8. a formal agreement or pact, esp a military one, between two or more countries to achieve a particular aim. 9. the countries involved in such an agreement. 10. a union between families through marriage. 11. affinity or correspondence in qualities or characteristics. 12. the state of being allied : the action of allying: nations in close alliance. 13. a bond or connection between families, states, parties, or individuals: a closer alliance between government and industry. 14. an association to further the common interests of the members specifically : a confederation of nations by treaty: the alliance of Western nations. 15. union by relationship in qualities : affinity: an alliance of industry and academia. 16. a treaty of alliance. in botany: a taxonomic category consisting of a group of related families; subclass. Examples: We need to form a closer alliance between government and industry. strengthen the alliance of western nations. Related Words: concord, concurrence, partnership, collusion, affiliation, relation, compact, union, support, engagement, betrothal, communion, cooperation, tie, participation, accord, federation, combination, collaboration, coherence. Synonyms: association; coalition, combination, bloc; partnership; affiliation. pact, compact. accord, convention, covenant, treaty. Synonym Study: Alliance, confederation, league, union all mean the joining of states for mutual benefit or to permit the joint exercise of functions. An alliance may apply to any connection entered into for mutual benefit. League usually suggests closer combination or a more definite object or purpose. Confederation applies to a permanent combination for the exercise in common of certain governmental functions. Union implies an alliance so close and permanent that the separate states or parties become essentially one. Origin: 1250–1300; Middle English aliance < Old French, equivalent to ali(er) to ally + -ance -ance. C13: from Old French aliance, from alier to ally. First Known Use: Noun: 13th century. History and Etymology: Noun: see ally. Source 1, Source 2.