when：表示一件事在某一時間發生，例I came home when 7o'clock.（我七點回家。）；while：表示一件事發生時另一件事也在發生，I came home while she was watching TV.（我回家時她正在看電視。）；among：在三者(或三者以上)中，區別於between(兩者中)；as soon as：一......就se call me as soon as you arrive at home.(請一到家就給我打電話。)。