英文两个单词的用法.join in 和join有什么不同?他们各用在哪里?请举个例子

join in sth/doing sth; join in with sb/sth
参加，假如 （活动）
She listens but she never joins in. 她只是听，但从不参与/发表意见
I wish he would join in with the other children. 但愿他能和别的孩子一块儿玩。
join 连接//加入
Join one section of pipe to the next.将一段管子与相邻的管子连接起来。
She joined the company three months ago.
谢谢！

join是加入（组织）；join in 等于：take part in：参加（活动）,如：
Tom joined the singing club two years ago.
Tom joined in the group singing.