"增长知识" 的英文表达是 "gain knowledge"。这个表达来源于英文 "gain" 和 "knowledge" 的结合，"gain" 意为 "获得"，"knowledge" 意为 "知识"。

下面是一些例句，请参考：

I read a lot of books to gain knowledge. (我读了很多书来增长知识。)

She spends a lot of time on the internet to gain knowledge about different topics. (她花很多时间在互联网上增长知识。)

He attends classes and workshops to gain knowledge about his field of work. (他参加课程和研讨会来增长知识。)