这里的 not 就是否定主语啊，没什么特殊用法。Not a = No。
Not a syllable was uttered by either.
= No syllable was uttered by either.
两个人都没有说一个字。
更多例句如：
Not a single soldier was killed. 没有一个士兵阵亡。
Not a word fell from his lips. 他什么话也没说。
Not a soul was to be seen. 一个人也看不见。
Not a sound reached our ears. 我们一点声音都听不见。
Not a single sound was heard. 一点声音也没听到。
Not a single book was left on the shelf. 书架上一本书也没有留下。
Not a word was spoken between them the whole time. 自始至终他们之间没说一句话。
Not a single one of her neighbours gave her any help. 没有一个邻居帮过她忙。
Not a sound was heard except the wind howling. 除了风的怒吼声之外其他什么声音都听不见。
注意，如果位于句首的 not a…不是主语，而是宾语，则通常用倒装语序。如：
Not a single word did she say. 她连一声也没有吭。
Not a word did they exchange during the meal. 在吃饭时他们一句话也没交谈。
