join in等于take part in。两者都有“参加”的意思，但join in多指参加某组织，成为其中的一个成员，take part in是指参加活动，因此take part in 表示的范围比join in要广，适用的情况也要多。
一、join in的含义及用法介绍
join in意为加入、参加活动。例句有：
1、I hope that everyone will be able to join in the fun
我希望每个人都能够加入进来，玩得开心。
2、Now and again he'd join in when we were playing video games.
我们玩电子游戏时，他偶尔会和我们一起玩。
3、We're going to play football. Do you want to join in?
我们去踢足球，你来不来？
4、It's no use egging him on; he's made up his mind not to join in the tournament.
他已拿定主意不参加比赛了，你再将他也没有用。
5、More and more people are beginning to join in the activity.
越来越多的人开始参加这项活动。
6、They join in the sport that interests them most.
他们参加他们最感兴趣的运动。
二、take part in的含义及用法介绍
take part in意为参加、参与。例句有：
1、The officer refused to let his men take part in the operation.
这军官拒绝让他的士兵参加这项军事行动。
2、They returned to take part in the season's opening game.
他们回来参加本赛季的开幕赛。
3、You can take part in activities from canoeing to bird watching.
你可以参与从划独木舟到观鸟等各种活动。
4、If you want knowledge, you must take part in the practice of changing reality.
你要有知识，你就得参加变革现实的实践。
5、Recently the students in our school all take part in sports.
最近我们学校的学生都参加体育运动。
