and,but,or三个单词都是连词，用法也比较灵活and 可以连接相同词性的单词或者短语，表示“和、还有”的意思，例如：you and me；也可以连接两个句子，这时候and 没有具体的意义，只是在句中起到一个连接的作用，例如：Please tell me if you get married,and I will come to congratulate you.but 也可以连接单词和短语，这时候的意思是“除了、不是...而是...”，例如：No one got passed in the hard exam but me.(除了) It's not because of mercy but love. 连接句子的时候意思是“但是”，例如：I know you're tired, but you still have to finish the work.or 连接单词或者短语时候的意思是“或者”，例如：Is he wearing a black sunglass or not? 在否定句中的意思是“和”，例如：During the first years they'd married, they didn't have any house or car. 连接句子时候的意思是“否则”，例如：Take an umbrella with you. Or you'll get wet in the coming rain.