1. a formal agreement between countries, groups, or organizations to work together for a common purpose
2. the state of being joined together in a cooperative relationship

Examples

• The two countries formed a military alliance to defend against common threats.
• NATO is a powerful alliance of democratic nations.
• The environmental groups created an alliance to fight climate change.
• Their business alliance proved very profitable for both companies.
• The political alliance between the parties lasted only two years.
• She built an alliance with other students to improve school policies.
• The alliance between the unions gave them more bargaining power.