两者均可表示“快”，在口语中，一般多用quick(尤其在需要用比较级或最高级时)，并且总是放在动词之后；若放在动词之前，一般用quickly。如：

Come quick(ly). There's been an accident. 快来，出事故了。

You get there quicker by bus.
你坐汽车去那儿会快一些。

He quickly changed his clothes.
他迅速地换了衣服。

The evening passed quickly. 晚上很快过去了。

He ran as quickly as he could. 他使劲地跑。

It gets hot quickly when the sun comes. 太阳出来了天很快热起来。

I was wondering how to get there quickly. 我想知道怎么能很快地到达那里。

He quickly availed himself of the opportunity. 他很快利用了这个机会。

After his wife's death he aged quickly. 他妻子死后他老得很快。

Relief was quickly sent to sufferers from the great fire.
救济物资迅速送到大火中受害人的手中。

How quickly time passed! It might have happened yesterday.
时间过得真快! 这仿佛是昨天发生的事似的。