阿=啊，一般用啊表示，for astonishment, understanding, just like oh! （表示你知道了，或者惊讶，或者突然间想起什么要说的，就用啊作为开头，然后写你要说的话。） 呵呵，就是普通的笑，like :) 嘻嘻，调皮地笑，laugh naughtily，like :D 哈哈，大笑，或者开心地笑，laugh happily 哈哈哈哈哈哈 ：you laugh because you think it is really funny and you cannot help stopping it.

哈哈

hmm,when you chat,you see 阿，maybe he wants to use 啊，just make mistakes.Now when we chat,we often ignore the difference of them.

阿 is always used for the names,such as 阿和，阿华，阿虎 etc. 啊 is used to show your strong feeings,for example,you love your country,you can say:"啊，我亲爱的祖国！" And usually when 啊 is used,you can see the punctuation “！". 呵呵、嘻嘻、哈哈 are all stand for laugh.There is small diffrence.嘻嘻 is a naughty laugh. 哈哈 is a big laugh.呵呵 is a kind and warm laugh.In fact you can use them as you like when you chat with others.It`s OK.

除了“阿”外，都是语气词。呵呵 哈哈 嘻嘻表示高兴，喜欢等意思。意思就是haaaa。但是现在有时候中国人和中国人网上聊天时，要是用到 呵呵 的话，别人可能会不高兴的，认为是在敷衍他。 啊，有惊讶的意思。比如：“啊，Jose，你竟然中了一亿欧元大奖。” 啊，也有表示同意，承认的意思。比如：“啊，对，我是中了一亿欧元的大奖”。 聊天时，“阿”要是以一个字出现，估计应该是想用“啊”，他写错了而已