Which of the two following sentences is more appropriate to say:

You must write fast.
You must write quickly.

I know the answer, but I need to explain it to somebody. It would be of great help to get expert inputs here.

2 Answers 2


Well, I'm not an expert that you are looking for, but let me put a bee in your bonnet. The adverb fast refers to the speed whereas quick refers to time. The confusion arises as in AmE, there's no qualm using an adverb fast whereas in BrE it's generally avoided. However, if you want your student to save time, use quick and if you want them to just write speedily, use fast!

There's something interesting. If I write an answer quickly it probably means that I knew the answer and I was quick to respond and write it without any doubt. On the other hand, writing answer fast has nothing to do with my knowledge. It's just my ability to write answer fast (may be blah-blah...)! Anyway, it's just my thought.

Surprisingly, COCAE shows equal number of results for both the phrases (write quickly/fast).

If we go by books, both are interchangeable. McMillian describes fast as quick and quick as fast!

fast - able to move quickly.
quick - able to move fast or do something fast

  • I agree with you completely, Maulik. I wanted someone to point this out; now I hope people carry this forward with their inputs. As a teacher instructing a classroom, I always say, "Write your answers quickly," because my focus is on completing their answers within the shortest time. Now, whether they actually write fast or not is of no concern to me. Mar 15, 2014 at 6:40
  • @NeilD'Silva I edited it. This may have some better input!
    – Maulik V
    Mar 15, 2014 at 6:45
  • Yes... I see. However, when my students face an exam, they always know the answers! So they are always 'quick' and 'fast' :D ... Mar 15, 2014 at 6:50
  • According to Cambridge Dictionaries Online, when looking at specifically British English, the adverb "fast" is defined, quite simply, as "quickly", and that same definition is found in OED. It would strike me as odd that all of those dictionaries would define fast so prescriptively. Is "fast" really limited to speed in Britain?
    – Cmillz
    Mar 15, 2014 at 6:52

Technically speaking, both are absolutely correct. The two words are essentially synonymous.

In the context of the statements, "You must write fast," and "You must write quickly," the intended meaning (I assume) is that the individual must complete the task of writing rapidly (in a short amount of time).

That meaning is conveyed by both "fast" (adverb definition 1.1) and "quickly" (definition 1), and so either word is acceptable and appropriate.

In a more formal setting, one could argue that "quickly" is a more appropriate word to use, as it is considered by many to be a less "simple" word. However, if that is the argument, then "quickly" is not a particularly fancy, intellectual word, either. In this setting, perhaps "rapidly" would be more appropriate.

In a conversational setting, however, the two words are completely interchangeable.


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