Is authority a synonym for alliance?

Answer 1

No; the most common uses of the words are not very much alike at all. Authority refers to an individual's or group's right to exercise jurisdiction or control over something. An alliance is a treaty or agreement that 2 or more parties undertake to work together for some common interest or goal.

However, some entities, in state governments for example, might have names similar to this: State Ice Cream Flavors Authority. A group of concerned citizens (or a group of groups) in another state without such an Authority might call themselves Sundae Alliance for the Preservation of Ice Cream Diversity. Even though there may be some similarities between these 'groups', they would not be considered identical. One actually has state sanctioned authority, and the other is most likely an advocacy group working for the protection of ice cream flavor diversity.