league、federation、union与alliance这些名词均含“联盟、同盟、联合会”之意。
league : 普通用词，指为了共同的利益而建立的地区性、全国性或国际性的联合组织，也指民间或半官方组织的联盟。
Who do you think will win the league championship this year?
你认为谁会获得今年的联赛冠军？
Liverpool were top of the Football League that year.
利物浦队是那一年的足球联赛冠军。
They are currently bottom of the league.
他们目前在联赛中垫底。
the League of Nations
国际联盟
federation : 泛指用条款固定下来的一切联合，尤指联邦政府。
the Russian federation
俄罗斯联邦
The federation of the six original Australian states took place in 1901.
1901年澳大利亚最初的6个州结成联邦。
He's against European federation.
他反对欧洲联盟。
union : 普通用词，指由若干个体结成的一个统一的整体。强调其永久性。
the Scottish Rugby Union
苏格兰橄榄球协会
the former Soviet Union
前苏维埃联邦
Meanwhile the debate on European political and monetary union continues.
同时，有关欧洲政治和货币联盟的争论还在继续。
She believes that the union (= marriage) of man and woman in holy matrimony is for ever.
她相信男女之间的神圣结合是永久的。
alliance : 普通用词，指对双方均有利的任何联盟。
a military alliance
军事同盟
NATO is sometimes called the Atlantic Alliance.
北约有时被称作大西洋同盟。
The three smaller parties have forged/formed an alliance against the government.
三个小政党结成反政府联盟。
Some of us feel that the union is in alliance with management against us.
我们中一些人感到工会和资方联合起来对付我们。