noun /ʌˈlaɪ.əns/
a) The state of being allied; the act of allying or uniting; a union or connection of interests between families, states, parties, etc., especially between families by marriage and states by compact, treaty, or league; as, matrimonial alliances; an alliance between church and state; an alliance between France and England.
The alliance of the principles of the world with those of the gospel. C. J. Smith.
b) Any union resembling that of families or states; union by relationship in qualities; affinity.
The alliance . . . between logic and metaphysics. Mansel.
Wikipedia foundation.