I've heard that you have to say "join someone" and "join in something". I am going to make up a few pairs of sentences below.
(1a) I will join you for John's birthday lunch tomorrow.
(1b) I will join in for John's birthday lunch tomorrow.
(2a) I will join you for his retirement party next week.
(2b) I will join in his retirement party next week.
(3a) I will join the international comic event next month.
(3b) I will join in the international comic event next month.
I think both (1) and (2) follow the correct usage. I believe that you can say "join an event" without adding a pronoun after "join" because you will participate in it. "join in an event" is the correct usage.
Am I using "join" and "join in" correctly in all my sentences?
Best Answer
1a and 2a are the only ones that sound correct to me.
to join-in means to take part in or to become involved in. It's something that's already happening when the subject joins in.
The dancing was already ongoing when "he" started.
The "fun" (party, festival, whatever) is already taking place.
I wouldn't use join in for a broad event. "She joined in the convention" would sound odd to me, because a convention isn't any one specific activity.
When talking about events and just using join, we wouldn't generally say join with the event itself. We join someone for the event.