看到每层楼都有不少点艹的，纠结了一下。还是自己去查下词典好了。
till 用作介词或连词时，完全可用until 代替 且更加正式。
只有Until能放句首。
《新牛津美语词典》：
第一句：The villagers didn’t realize how serious the pollution was until all the fish died in the river.
第二句：Not until all the fish died in the river did the villagers realize how serious the pollution was.（倒装句）
第三句：Not until his son came back from school did he go to bed.
第四句：It was not until his son came back from school that he went to bed.（强调句）
强调句：在英文中，句子的主语、宾语、状语都可以写进一定的句式里以表示对它的强调。
倒装句：英语的基本语序是“主语谓语”，假如将谓语的一部分或全部放在主语之前，这种语序叫倒装。倒装既是一种语法手段，也是一种修辞手段，用于表示一定的句子结构或强调某一句子成分。
