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Slow has the adverb slowly. I tend to use fastly as the adverb for fast.

However, it is underlined in most spell checkers I use, which makes me wonder about the existence of this word.

Is fastly a correct word? If not, what should be used instead, and why is that different from its antonym?

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No need to apologize, this site is for people like yourself that are interested in improving. The sad fact is that many native English speaks don't understand "trivial" concepts, and don't care about being correct. You should be proud of the fact that you even asked. –  Jed Daniels Aug 20 '10 at 1:29
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Those native English speaks ought to be ashamed of themselves. –  delete Aug 20 '10 at 2:01
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Check out this video from Merriam-Webster on flat adverbs: merriam-webster.com/video/… –  Phong Jan 9 '12 at 18:23

9 Answers 9

up vote 41 down vote accepted

There is no need for "fastly" because "fast" is both an adjective and an adverb. So, "I ran fast" is completely correct.

The existence of "fast" as an adjective does not preclude the future development of a word "fastly", but it does hinder it.

One might note that the corresponding adjective "slow" does take the -ly suffix, but this has no impact on the behavior of "fast". (There is also no real reason why, for example, we have warm/warmth, but cool/coolness. Semantically related things sometimes have similar morphological patterns, and sometimes not.)


One interesting thing worth noting (that was brought up in a comment by Jimi Oke) is that there are cases of adjectives with identical adverbs that also have an -ly form; for example, we have "right" and "wrong" as adjectives and adverbs, but we also have "rightly" and "wrongly". In such cases, the -ly form has carved out its own semantic niche; the adverb "right" and the adverb "rightly" cannot be used interchangeably in every situation. I can say "turn right" and "rightly so", but I can't exchange them in either sentence.

With normal adjectives that cannot become adverbs without -ly, usually the -ly just transparently makes the adjective adverbial — it doesn't have its own separate semantic nuances (e.g. "quickly" simply means "in a quick manner").

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Er...I beg to differ. I drove quickly, but the car was fast. Fast is an adjective not an adverb. The adverb is quickly. –  Brian Hooper Aug 19 '10 at 22:24
    
You could, however, be stuck fast. I've no idea what part of speech 'fast' is in that context. –  Brian Hooper Aug 19 '10 at 22:25
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As I said, "fast" can be an adjective or an adverb. "The car was fast. The car drove fast." Both are correct. You can even check the dictionary if you don't trust me: dictionary.reference.com/browse/fast . –  Kosmonaut Aug 19 '10 at 22:36
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Imagine if a pedant insisted that you could not say "How fast does this car go?" because you ought to say "How quickly does this car go?" I think "quickly" actually sounds silly there. –  Kosmonaut Aug 20 '10 at 20:28
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@jjackson: I am 100% certain. Any dictionary will back this up. –  Kosmonaut Jan 28 '11 at 1:56

Fast is an adverb as well as an adjective, so you wouldn't use fastly. Another common adverb that doesn't follow the pattern of ending in ly is well, not the expected goodly, which is actually an adjective and means a large quantity, e.g. a goodly sum.

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Per etymonline, fastly is the 'former adverbial form of fast (adj.), from O.E. fæstlic "firm, fixed, steadfast, resolute;" obsolete in 19c., simple fast taking its place.'

There you go folks, so much for logic...

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Oh, fastly is a word alright. It just happens to be an obsolete one.

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This reminds me of how small children extrapolate grammatical constructions in seemingly logical ways, except English is not always that logical.

So my daughter (3¾) will correctly say "I colour in neatly" or "I'll do it carefully", but then also "It comes lastly" "I can hop bigly" "Go farly" "Squeeze me hardly" etc.

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The adverb form of fast is irregular. It is one of several exceptions, as is "well" as mentioned by Dena A.

a fast runner   /    run fast
a hard worker   /    work hard
a bad smell     /    smell bad

etc. etc. etc.

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Small note... bad is not an irregular adverb in this case, it is an adjective with irregular verb behavior (see rule 2 of grammarbook.com/grammar/adjAdv.asp). You could say "smell badly" to talk about being unable to smell properly. –  Kosmonaut Aug 21 '10 at 20:09

"Fast" can also mean to hold onto in a strongly, and "fastly" is the adverb of that word. E.g. "The crew held fastly onto the hand-rail of the boat as it rolled in the storm"

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I wouldn't say that, and google gives 118 hits for "held fastly", as against 298 000 for "held fast". Another adjective which is also an adverb is "hard". "Hardly" exists, but has a completely different meaning. –  Colin Fine Aug 20 '10 at 12:24
    
Sorry, but "fastly" just isn't a word. You drive fast. You hold fast to the handrail of the boat. You hold fast to an idea. You can also drive quickly, but that's the same as driving fast. –  Dena A Feb 7 '11 at 18:50
    
As said from Kosmonaut too, fast is already an adverb, and the suffix -ly is used to create an adverb from an adjective. –  kiamlaluno Feb 7 '11 at 18:51

Though word fastly used in many places (you can find many results by searching Google) but still it is not correct.
For reference see the definition of word fast from WikiDictionary

See the post wrong / fast-- adverbs with no 'ly' ending to learn more.

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No, "fastly" isn't a word. "Quickly" is used instead.

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protected by RegDwigнt Apr 30 '12 at 13:10

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