678　to say nothing of，not to speak of，not to mention和let alone

◎ 这几个短语均意为“更不用说，更谈不上”，通常用于否定句，有时也可用于肯定句，对其后的相关部分进行强调。

① to say nothing of，not to speak of和not to mention后接名词或动名词。

He knows only a little about English grammar，to say nothing of English rhetoric. 他对英语语法知道得很少，更谈不上英语修辞了。

② let alone后接名词或动词。

I have never heard of her before，let alone know her well. 我以前从没听说过她，更不用说了解她了。