(1)   An alliance of nations joining together to fight a common enemy
(2)   In World War I the alliance of Great Britain and France and Russia and all the other nations that became allied with them in opposing the Central Powers
(3)   The alliance of nations that fought the Axis in World War II and which (with subsequent additions) signed the charter of the United Nations in 1945


From alien, alier (French alier), from , from + . Compare alligate, allay, alloy and ligament.


  1. To unite, or form a connection between, as between families by marriage, or between princes and states by treaty, league, or confederacy
  2. To connect or form a relation between by similitude, resemblance, friendship, or love.
    • These three did love each other dearly well, And with so firm affection were allied. --Edmund Spenser.
    • The virtue nearest to our vice allied. --Alexander Pope.

Usage notes

  • Generally used in the passive form or reflexively.
  • Often followed by to or with.


  1. One united to another by treaty or league; — usually applied to sovereigns or states; a confederate.
    • The German soldiers and their Russian allies. -- Thomas Babington Macaulay.
  2. Anything associated with another as a helper; an auxiliary.
    • Science, instead of being the enemy of religion, becomes its ally. --Buckle.
  3. Anything akin to another by structure, etc.