盟 oath

I take an an oath to clean my plate until it's sparkley bright. But I MAY break the oath.

alliance ★☆☆☆☆ NP
同 (same) + 盟 (oath) = 同盟 (alliance)

an alliance, league, union (usually used with military alliances: NATO, UN Security Treaty nations, the Warsaw Pact alliance, etc.)

a federation ☆☆☆☆☆ NP
連 (take with / inform of) + 盟 (oath) = 連盟 (a federation)

a federation : unlike the related terms 連合 (れんごう）　and 同盟　（どうめい）, 連盟 is made of individual people, not federated nations or gangs. れんめい is more like volunteers. Baseball clubs, Chess associations, the League of Women Voters, are 連盟。