Alliance/əˈlaɪəns/ Definition 1 of 4Pro Tip 1/3Common Purpose Alliances are always for achieving a common aim; they unite members' efforts. The companies' alliance aimed to develop cleaner technologies. Pro Tip 2/3Often Formal Alliances between organizations or countries are typically formal agreements. The nations signed a formal alliance for mutual defense. Pro Tip 3/3Strength in Numbers Alliances suggest strength by showing unity among the members. Their alliance gave them the majority in parliament.