They fell in love with each other at first sight

问题描述:

They fell in love with each other at first sight
为什么序数词first前不加the啊.

at first sight是一个固定词组,表示“一看到...就”,而at the fitst sight则是在叙述时间是其强调作用.原句的意思是“他们一见钟情.”好麻烦啊。。我还以为错了呢。。