A symmachia (συμμαχία|symmachia) is and was in ancient times a military treaty between independent polities covering both offense and defense. In modern Greek the word also can mean an alliance among political factions to form a political party.
A late alternative to alliance was koinon, "the common thing", meaning the common alliance. Koinon had many other public things in its semantic repertory, but its use with the ethnic name of the chief ally left no doubt.
See main article: List of ancient Greek alliances.