Quickly is the usual adverb from quick. * quickly 为源自 quick 的常用副词：◆I quickly realized that I was on the wrong train.我很快意识到我坐错了火车。◆My heart started to beat more quickly.我的心开始跳得快起来。
Quick is sometimes used as an adverb in very informal language, especially as an exclamation.在日常用语中，quick 有时用作副词，尤作感叹语：◆Come on! Quick! They'll see us!快点儿吧！快！他们会看见我们的！Quicker is used more often. * quicker 更常用：◆My heart started to beat much quicker.我的心跳开始大大加快。◆The quicker I get you away from here, the better.我越快送你离开此地越好。
Fast is more often used when you are talking about the speed that somebody or something moves at.指某人或某物移动的速度多用 fast：◆How fast can a cheetah run?猎豹奔跑的速度有多快？◆Can't you drive any faster?你难道不能开快点儿？◆You're driving too quickly. There is no word fastly.没有 fastly 这个词。