Federation

A federation is a political system where constituent units (states, provinces, republics) retain significant self-governance while delegating powers like defense and foreign affairs to a central government. The opposite is a unitary state (centralized), like Japan or France.

Major federations include USA (50 states), Germany (16 states), Russia (85 federal subjects), Brazil (26 states), India (28 states), Australia (6 states), Canada (10 provinces), and Switzerland (26 cantons). About 25 countries are federations, tending to be large or multi-ethnic nations.

Knowing that a country is a federation narrows it to about 25 countries. 'Federation + Africa' means Nigeria, Ethiopia, Somalia, Sudan, South Sudan, or Comoros (6 countries).