Alliance

An alliance is a relationship among people, groups, or nations that have joined together for mutual benefit or to achieve some common purpose, whether or not an explicit agreement has been worked out among them. Members of an alliance are called allies. Alliances form in many contexts, including political alliances, military alliances, and business alliances. A formal military alliance is not required for being perceived as an ally — co-belligerence, fighting alongside someone, is enough. According to this usage, allies become so not when concluding an alliance treaty but when struck by war.
==See Also==
*Alliance at Wikipedia