How to say "federation" in Japanese

• 連邦れんぽうJLPT N1approx.Common
  nounThe political sense: a country formed by member states united under a central federal government; this is the word for federations of states, and it also covers 'confederation' and 'commonwealth'.
  アメリカ人あめりかじんは連邦れんぽう税ぜいと州税しゅうぜいの両方りょうほうを払はらっている。↗

  Americans pay both federal taxes and state taxes.
• 連盟れんめいJLPT N1approx.Common
  nounA league or alliance of organizations, teams, or societies rather than a union of states; choose this for sports leagues and federations of clubs or professional groups.
  某ぼう連盟れんめい元会長もとかいちょうが背任はいにんの容疑ようぎで逮捕たいほされました。↗

  The former president of a certain association has been arrested on suspicion of breach of trust.
• フェデレーションCommon
  nounThe katakana loanword, used where the English term itself is current, especially in technical fields such as IT; for general senses the native words are better choices.
• 合衆国がっしゅうこくCommon
  nounMeans a federal state itself — a country formed by united member states — so it suits 'federation' only in that concrete national sense; it appears in the Japanese name of the United States.
• 連合会れんごうかいCommon
  nounA federation of associations: an umbrella body formed when smaller organizations band together. It fits 'federation' for such alliance-of-groups bodies, not for a political union of states.

Use 連邦 for a political union of states, 連盟 for leagues of organizations or teams, 連合会 for umbrella associations, 合衆国 for a federal state itself, and 「フェデレーション」 for the loanword in technical contexts.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

• 連邦れんぽうfederation (of states)
• 連盟れんめいleague
• フェデレーションfederation
• 合衆国がっしゅうこくfederation
• 連合会れんごうかいassociation
• 連合体れんごうたいfederation
• 連邦国家れんぽうこっかfederal state