Join的基本词义是“加入某个党派或社会团体，从而成为该党派或团体的一员”。例：
When did they join the conservation organization？
他们是什么时候参加环保组织的？
The prodigy joined the International Association of Poets，
Playwrights，Editors，Essayists and Novelists（PEN）when he was only fourteen years old．
这位天才在十四岁时便成为国际笔会会员。
Join in的意思是“参加某项运动或活动”，例如参加讨论、游行、罢工等。例：
More than ten thousand workers have joined in this strike．
有一万多名工人参加了此次罢工。
All of us will join in the celebration of the victory of World War Ⅱ．
我们全都参加这次庆祝世界二次大战胜利的活动。
There were many extracurricular activities，but Peter never joined in．
尽管有很多课外活动，但彼德从不参加。
Join to的意思是“和…接触”、“与…相连”。例：
Our house is joined to Mr．So's．
我们的房子和苏先生的房子相连。
请注意，join之后如接 oneself再加to，就表示“参加”、“加入”的意思。如：
To my surprise，Mr．Li joined himself to the opposite party last month．
令我惊奇的是，上个月李先生竟然参加了反对党。
