alliance

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A close association of nations or other groups, formed to advance common interests or causes.
• noun A formal agreement establishing such an association, especially an international treaty of friendship.
• noun A connection based on kinship, marriage, or common interest; a bond or tie.
• noun A long-term association of two or more animals of the same species, in which members cooperate for a purpose such as gaining access to mates or defending territory.
• noun Close similarity in nature or type; affinity.
• noun The act of becoming allied or the condition of being allied.

from The Century Dictionary.

• noun The state of being allied or connected; the relation between parties allied or connected.
• noun Connection by kindred.
• noun Union between nations, contracted by compact, treaty, or league. Such alliance may be defensive, that is, an agreement to defend each other when attacked; or offensive, that is, an agreement to make a combined attack on another nation; or it may be both offensive and defensive.
• noun Any joining of efforts or interests by persons, families, states, or organizations: as, an alliance between church and state.
• noun The compact or treaty which is the instrument of allying or confederating: as, to draw up an alliance.
• noun The aggregate of persons or parties allied.
• noun In botany, a grade intermediate between class and order: the equivalent in Lindley's classification of the more recent term cohort.
• noun In zoology, a natural group of related families; a superfamily or suborder.
• To unite by confederacy; join in alliance; ally.

from the GNU version of the Collaborative International Dictionary of English.

• transitive verb obsolete To connect by alliance; to ally.
• noun The state of being allied; the act of allying or uniting; a union or connection of interests between families, states, parties, etc., especially between families by marriage and states by compact, treaty, or league
• noun Any union resembling that of families or states; union by relationship in qualities; affinity.
• noun The persons or parties allied.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun uncountable The state of being allied.
• noun countable The act of allying or uniting.
• noun countable A union or connection of interests between families, states, parties, etc., especially between families by marriage and states by compact, treaty, or league.
• noun countable Any union resembling that of families or states; union by relationship in qualities; affinity.
• noun The persons or parties allied.
• verb obsolete To connect or unite by alliance; to ally.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the act of forming an alliance or confederation
• noun the state of being allied or confederated
• noun a formal agreement establishing an association or alliance between nations or other groups to achieve a particular aim
• noun a connection based on kinship or marriage or common interest
• noun an organization of people (or countries) involved in a pact or treaty