Cases of word usage

1) a formal union of states etc (confederacy)

2) (the act of forming) a political union of states (confederation)

3) a union of two vowel sounds or vowel letters e.g. as in pipe /paip/ (diphthong)

4) (an act of) forming a political union of several states for control of foreign affairs, defence etc by the central (Federal) government but keeping regional (State) government for other things such as education (federation)

5) the authority given to representatives by voters, members of a trade union etc (mandate)

6) (an instance of) a legal union of a man and woman as husband and wife; the state of being married (marriage)

7) to be a picture, sign, symbol or example of (of a person, thing); to act officially for (a person), e.g. as a lawyer, member of parliament, union leader etc (represent)

8) to organize (workers) into a trade union (unionized)