fast : 常指人或物持续地高速运动，强调运动的方式。
- fast cars
- a fast swimmer
- Computers are getting faster all the time.
- The fast train (= one that stops at fewer stations and travels quickly) to London takes less than an hour.
quick : 特指瞬时动作，强调动作敏捷迅速；也指匆忙的行为，而不暗示速度很快。
- It's a quick journey.
- I had a quick coffee and left the house.
- I only had time for a quick glance at the paper this morning.
- He scored three goals in quick succession (= one after the other in a short time).
- Could I have a quick word (= speak to you for a short time)?
- Quick as lightning (= very quickly), he snatched the book and ran out of the room.
- The 1990s were a period of rapid change/growth.
- I was startled by a rapid movement to my left.
- His response to the accusation was rapid.
swift : 正式用词，强调非常迅速，往往含动作轻快敏捷之意。
- The police took swift action against the rioters.
- Thank you for your swift reply.
- The gazelle is one of the swiftest and most graceful of animals.
hasty : 多指匆忙、草率或仓促的行动，着重缺乏深思熟虑。
- He warned against making hasty decisions.
- Now let's not leap to any hasty conclusions.
- We saw the rain and made a hasty retreat into the bar.
- I think perhaps we were a little hasty in judging him.
prompt : 主要指动作迅速，毫不拖延，含“快得令人愉悦”的意味。
- They've written back already - that was a very prompt reply.
- They're usually fairly prompt in dealing with enquiries.
- Try to be prompt because we'll be very short of time.
speedy : 指人或物或其运动、活动时，着重极度的快捷，多含匆忙意味。
- He's a very speedy worker.
- We need to take speedy action/make a speedy decision.
- Everyone is hoping for a speedy end to the conflict (= hoping that an end to it will happen quickly).
- We wished her a speedy recovery from her illness (= that she would get better quickly).
instant : 指某事很快发生或急待解决，含刻不容缓之意。
- In an instant her mood had changed.
- The startled boy froze for an instant, then fled.
- "Stop that noise this instant (= now)!"
- I'll call you the instant (= as soon as) I get home.