“换言之”的意思是“用别的话来说”，常用在你想把前面的意思说得更清楚的时候。

The meaning of "换言之" is "in other words," often used when you want to clarify the previous statement.

它比较正式，多出现在文章或书面语里。

It is more formal and often appears in articles or written language.