noun
federation
fed-uh-RAY-shun/ˌfedəˈreɪʃn/
A union formed by bringing separate bodies under common authority.
The three regions form a federation with a shared central assembly.

Etymology
Latin foederare meant 'to league together' and came from the word for a covenant. Federation names the resulting union: members joined by agreement under shared authority.
In context
Article one says union of states. It means Indian federation is not the result of agreement by the states.
More examples
- Each state in the federation keeps its own legislature.
- The federation sets safety standards for its member clubs.
- Several trade unions join together in a national federation.
Forms
federation · federations
federal adjective — Relating to a federation's shared government.
federate verb — To unite under a shared authority.
Similar words
- confederation
- Usually gives member bodies more independence from central authority.
- union
- Broader term that does not necessarily imply shared authority.
- alliance
- Emphasizes cooperation among members rather than a common governing body.