而federation是各個部分壹起組成的主權國家，是聯邦國家。比如美國。
對比如下:
1.都有組織工會的意思
A--union - an organization of employees formed to bargain with the employer;
比如工會 LABOR UNION
B--federation-an organization formed by merging several groups or parties
比如:美國勞工聯合會American Federation of Labor
2.federation 有官方的政治上的壹種聯合相比於union- a union of political organizations
3.union有配對的意思 - the act of pairing a male and female for reproductive purposes; "the casual couplings of adolescents"; "the mating of some species occurs only in the spring"
而federation沒有這個意思.
4.union有合並的含義 - the state of being joined or united or linked; "there is strength in union"而federation沒有這個意思.
5.union有結合結婚的含義 - the state of being a married couple voluntarily joined for life 而federation沒有這個意思.
綜上UNION的含義比FEDERATION更寬泛壹點.
理解單詞的含義可以幫助妳在不同的場合使用合適的詞.加油!