We use "join", "participate in", and "join in" much less often than you use 参加 in Mandarin. For most places where you use 参加, we use other verbs. We usually "go to" or "attend" scheduled events, like parties, meetings, weddings, and graduation ceremonies. If you are in the audience at a roundtable or colloquium, you "go to" it or "attend" it. If you are on the stage, you are "speaking at" the roundtable or "participating in" it. We "join" GROUPS OF PEOPLE; we usually don't "join" events. You can join a club or a team, but not a party or a meeting. "join in" and "participate in" both refer to ACTIVITIES, but they have different grammar. Don't put nouns after "join in": "I saw several people singing a song, and I joined in"= ...and I started singing with them. (if you wanted to use "join" instead of "join in", you would say "I joined THEM", NOT "I joined IT." You join PEOPLE: you don't join an activity.) "When Bob and Sam started to explain English grammar to Jill, Sally joined in and gave Jill some useful examples." I participated in the race= I ran in the race/ I competed in the race/ I was a contestant in the race. I participated in the bake sale= I sold cookies. It DOESN'T mean "I bought cookies". I participated in the presentation= I was one of the people who GAVE the presentation, NOT one of the people who heard it.

1. JOIN - usually followed by either an object pronoun (ex. them or me) or noun (ex. the others, chess club, etc) 2. JOIN IN - Not used often - to avoid using JOIN IN: replace IN with the thing being joined a. Why don't you JOIN IN? VS Why don't you JOIN [object]? - In the first sentence, the thing being joined is usually gestured to, so people know what is being joined although it's not explicitly mentioned. -In the second, the object (the thing being joined) is stated explicitly, so it doesn't need to be physically present or happening in the moment. 3. PARTICIPATE -is a more formal word... mostly used in academic and work settings, so you probably won't be using it in everyday conversation 4. As someone on Hinative explained well, JOINing is more passive and PARTICIPATing is active. Sooo, if you participate, you are doing something. If you join, you are just becoming part of something, it doesn't imply that you are actively engaged.

I am borrowing this answer from English Language Learners Stack Exchange: "Join in" idiomatically means to "get involved" with something, for example: I joined in with the laughter. "Join" alone means to unite or connect with someone or something. Ex. You join the math club. You are a participant in the math club, so you participate in its activities. Ex. You join in the discussion of the math club members. You participate in the club discussions. Hope this helps. L

Sometimes logic cannot explain these differences. We have to develop a gut feeling that only comes from being around native speakers who use these phrases...

"Join" often means to become a part of something or to meet, as in: "Please join us tomorrow." "Join in" is usually used when there is no phrase following. For example, "Why don't you join in?" If a word or phrase is following, "join in" is not usually used (e.g. "Join the party"). "Participate" indicates interaction and activity. For example, "Please participate in the discussion. We need your input."