Dear Binh Mai， 你好: 【可是】和【但是】基本意思差不多： 【可是】多用于口语，表达语气更委婉，且经常作为进一步的补充说明、陈述或解释原因。 比如: 我很想跟你去超市，可是我下午有事情，对不起啊！ 我记得我就放在这里的，可是现在就是找不到。 【但是】口语和书面语都可以用，表达语气很坚定，通常直接表示和前面一句话相反的对立面，且强调后半部分。经常与虽然连用。 比如：虽然妈妈很生气，但是她没有责备我们。（我们以为妈妈一定会责备我们，事实与预期的完全相反） 虽然这件衣服很漂亮，但是我觉得它不值这个价钱。（漂亮的衣服不一定值这个钱，和漂亮就应该很贵形成对立面） 试试做一些练习吧：用【可是】和【但是】 1.你真的要走吗?_________饭已经做好了！ 2.外面在雨很大，_______我没有带伞。 3.虽然这次比赛你输了，________你的努力大家都看到了！ 4.虽然作业写完了，_______还是被老师批评了一顿。 希望对你有帮助哦，Thanks ~

没有特别大区别，“但是”常与虽然连用。虽然他是个小孩子，但是他吃的特别多。

I hate to be the bearer of bad news... but there isn't really much of a difference between 但是 and 可是 in everyday speech. Both have the same meaning, and the two are almost interchangeable. I know, back in school, we learned about the basic sentence constructs, "虽然...但是..." being one of them (along with the well-known "一边...一边...", among others), but that is school. In everyday conversations, how many of us actually start a sentence with "虽然" just so that we can use the "但是" ? Most of the times, the "虽然" is simply dropped. For simplicity's sake, sometimes, certain parts can be, and are omitted/neglected/abbreviated in Chinese. In fact, Chinese tend to use "但是" more so than they would use "虽然...但是...", "可是", "不过" or "但...". But the others are there to add variances to your sentences. That isn't necessarily a bad thing. The only thing that I'll like to point out is that "虽然...但是..." is the more complete expression, and it has a more formal feel to it. ps: Natives, no matter the language, they have their own habit of saying certain things. For people who are non-native to that language, we'll just have to adapt.

語氣上就有明顯不同了 ex:朋友約妳晚上吃飯,而妳的回答是: 1."可是"我有其他事情 -> 對別人比較委婉地拒絕 2."但是"我有其他事情 ->對別人比較堅定的拒絕