我们一起去吧 吧 is an interjection. When it is used in a sentence which requests something or asks someone to do something, it makes the sentence sound less commanding or bossy, or makes the sentence contain some kind of emotion. Examples: 1. 请你把这件事情做完。-- it sounds more like a boss speaking to a subordinate. 请你把这件事情做完吧！-- it sounds more like a coworker speaking to its counterpart. 2. 我们一起去北京旅游。-- it's hard to tell the tone of the speaker if you only see the sentence. You have no idea about his real attitude for the trip unless you HEAR the sentence from him. 我们一起去北京旅游吧！-- it sounds like the speaker is really excited, happy for the trip. 欢迎你去玩儿 it means "welcome you to visit somewhere". 欢迎 (welcome) 你( you ) 去 (go to) 玩 (play) 儿 (no meaning). Examples: 欢迎你来我家玩儿！ 欢迎你去中国！ 欢迎你来上海！ I guess you might not understand "儿". This word actually means nothing. People in Northern China like use 儿 at the end of some sentences. Remember, not in all sentences, just in some. Don't ask me which kind of sentences because I can't tell the rule either. When I speak, I just know. I'll give you some examples: 1. 你在哪？ 你在哪儿？ 2. 去我家玩。 去我家玩儿。 3. 这首歌一点也不好听。 这首歌一点儿也不好听。 Each sentence of the above three groups is correct, but people in Northern China prefer the second sentence.

1 the sentence 欢迎你去玩儿 is the same as 欢迎你去玩. It means you are welcomed to my place. 儿 is just a retroflexion and it'd be totally OK if you can not pronounce that 'cause even most sountherners in China can neither. Actually, there's no 儿 the retroflexion in the standard Chinese. And besidese, I don't think the sentence is totally right, 'cause usually we'll say 欢迎你来玩儿. So have you seen the difference? ‘Cause if I say that to you, it probably means I am the host of that place or locals in the area you'll go to or you are new in. 来means you coming up to me instead of going to some place further from me. I haven't heard 去 used like that from North to South China. 2 The sentence 我们一起去吧 means Let's go or There we go. 吧 is just the interjection Chinese prefer. And it feels like you want somebody to do what you told him to or you just ask someone do something they are likely agree to. such as 我们去吃饭吧!=Let's go a meal, what do you say? (you want someonedo what you told him to) 今晚吃面条吧!=What do you think we have noodles for supper? 你就把这个包包买下来吧！= What do you think buy that purse?

欢迎 你 去 玩儿 = welcome to go there to have fun 我们 一起 去 吧 = let's go together 吧 = encouraging particle