eg：Light travels fast than sound.

　　the+比較級：

　　eg：The sooner，the better.

　　(1)當……的時候：while，when，as ;

　　when：強調一件事情正在發生的時候，另外一件事情突然發生;

　　eg：When I was watching TV, my mother came back.

　　while：強調兩個動作同時進行，一邊……一邊……;

　　eg：My father is cooking while my mother is reading newspaper.

　　as："隨時間推移"

　　eg：As time went by, the days became longer and longer.

　　(2)一……就……：as soon as，主將從現;用directly，immediately， instantly連接兩個句子;一些名詞如the minute，the moment，the instant也可表示;no sooner… than，hardly… when后面的句子需要倒裝;

　　eg：I will write to you the moment/minute I arrived in Paris.

　　(3)特殊單詞：by the time that，every/each time(使用時后面不要再加when)

　　(4)till&until：

　　① 肯定形式表示的意思是"做某事直至某時"，動詞必須是延續性的;

　　否定形式表達的意思是"直至某時才做某事"，一般用until，動詞為延續性或非延續性都可以;

　　eg: I slept until midnight.

　　Wait till I call you.

　　She didn't arrive until 6 o'clock.

　　② Until可用于句首，而till通常不用于句首，通常用于句中;

　　eg: Until you told me, I had heard nothing of what happened.

　　eg：As you sleep you pass through a sequence of sleep states—light sleep, deep sleep and REM (rapid eye movement) sleep—that repeats approximately every 90 minutes.