Expressing "however" with "ran'er"

然而 (rán'ér) is a conjunction used to express "however" or "but." The difference between 然而 (rán'ér) and 可是／不过 is that it's more formal (?) 

Structure

Statement, 然而 + [Unexpected Outcome/Contrary Statement]

Examples

• 老师已经把话题解释了好几次, 然而，学生还不明白. The teacher explained the topic multiple times, however, the students still did not understand.
• 我每天都跟他聊天，然而我不记得他的名字. I speak to her everyday, however, I don't remember her name.
• 我很喜欢那件裤子. 然而，我买不起. I like those pants a lot. However, I cannot afford them.