第3个回答 2010-12-22
as is commonly the case 是一个“非限制性定语从句”,翻译出来是“这是通常的情况”。其中 as 是“关系代词”,意思是“这事”。作定语从句的主语,is 是系词,commonly 是状语,the case 是表语,即定语从句本身是一个“主系表句型”。
又例: Many people do exercises in the morning, as is commonly the case. (很多人做晨练,这是通常的情况。)还有一种差不多的表达方式是 as is often the case (这是常有的事)。例如:He comes to the classroom in the early morning, as is often the case. (他一大早就来到教室,这是常有的事。)
从语法上严格来说,在 as 之前应该有一个逗号,但是人们为了节省时间,往往把逗号扔了。