“加入工会”常见的英文表达是 “join a trade union” 或 “become a member of a trade union”。
“join a trade union”：这是最直接、常用的表达方式，“join”表示加入某个组织，“trade union”即工会。
“become a member of a trade union”：这种表达更正式一些，明确指出成为工会的成员。
例如：
Many workers choose to join a trade union to protect their rights and interests.（许多工人选择加入工会以保护自己的权利和利益。）
He decided to become a member of a trade union to have a stronger voice in the workplace.（他决定加入工会，以便在工作场所拥有更大的话语权。 ）