alliance · noun C /əˈlɑɪ.əns/
alliance
C2 an agreement between people, countries, political parties, etc., to work together to achieve something
Dictionary examples:
The mayor wants to form an alliance with local business leaders.
an alliance between the countries/families/groups
Learner example:
They took the opportunity and made an alliance with all the cities in Southern Greece under their command. (Certificate in Advanced English; C1; Greek)