1. 工会
    A union is a workers' organization which represents its members and which aims to improve things such as their working conditions and pay.

    e.g. I feel that women in all types of employment can benefit from joining a union.
           我认为女性无论从事什么工作，加入工会都是有好处的。
    e.g. ...union officials.
           工会官员

2. 联合；合并
    When the union of two or more things occurs, they are joined together and become one thing.

    e.g. In 1918 the Romanian majority in this former tsarist province voted for union with Romania.
           1918年，这个前沙皇统治的省份中占了多数的罗马尼亚人投票赞成与罗马尼亚合并。

3. 联盟；联合体
    When two or more things, for example countries or organizations, have been joined together to form one thing, you can refer to them as a union .

    e.g. Tanzania is a union of the states of Tanganyika and Zanzibar.
           坦桑尼亚是坦噶尼喀和桑给巴尔两个政体组成的联合国家。
    e.g. ...the question of which countries should join the currency union.
           关于哪些国家应该加入货币联盟的问题

4. 婚姻
    The marriage of two people is sometimes referred to as a union .

    e.g. Even Louis began to think their union was not blessed in the eyes of God.
           就连路易斯都开始认为他们的婚姻并没有受到上帝的祝福。

5. （用于名称中）俱乐部，协会，联合会
    Union is used in the name of some clubs, societies, and organizations.

    e.g. The naming of stars is at the discretion of the International Astronomical Union.
           给星体命名是由国际天文学联合会决定的。
    e.g. ...the Mothers' Union.
           母亲联合会