till /和until在表達方式和意義上的特殊性：until是till的強調形式，但是它們表達的意義是相同的，都表示"直到某時"。不過，當主句是否定句時，它引出的意思是"直到（某時）（某動作）才（發生）" ，這時候常會出現"not until …"的結構，如果將 "not until …"的結構放在句首，那麼主句要寫成倒裝句。例如：
He didn't go to sleep until 12 last night .
他昨晚直到十二點鐘才睡覺。
They didn't realize their fault till we pointed it out to them .
直到我們向他們指出了他們的錯誤，他們才意識到。
Not until we pointed out their fault to them did they realize it .
直到我們向他們指出了他們的錯誤，他們才意識到。
但是，當主句是肯定句時，它引出的意思是"直到（某時某動作停止了）" 。例如：
The students made much noise till the teacher came into the classroom .
直到老師走進教室學生們才停止了大聲喧譁。
The young couple were very happy until they used up all their money .
那對年青夫婦直到花光了所有的錢才沮喪起來。
另外，until 可以放在句首而till則不行。我們可以説：Until they used up all their money, the young couple were very happy .我們卻不可以説：Till they used up all their money, the young couple were very happy .
