He might think it's strange to eat insects, but the fact is it's a common practice in some cultures.

the 是定冠词，用于特指某个事物或情况。 fact 是名词，意思是"事实"，指真实存在或发生的情况。 is 是系动词 be 的第三人称单数现在时形式，用于连接主语和表语。 the fact is 是一个固定表达，意思是"事实是"，用于陈述一个客观真实的情况。