The whole sentence is

We show that this approximation, when coupled with an active learning strategy, is fast but accurate.

is there a not missing before accurate? Or is the meaning fast and accurate?

  • 3
    I think the meaning is exactly as stated. Why would you think otherwise? Jun 5, 2018 at 13:08
  • That's the thing, I don't understand the exactly stated meaning, that's why I ask. I use and know the word but as in contrast/opposite to something being fast but accurate makes no sense to me. Is it both or is it only fast but not accurate? and if it is both why wasn't the word and used?
    – Hakaishin
    Jun 5, 2018 at 13:11
  • 1
    The normal expectation is that speed and accuracy are in opposition -- that improving one makes the other worse. The "but" emphasizes that this expectation does not hold in this case.
    – Hot Licks
    Jun 5, 2018 at 13:17

3 Answers 3


Sometimes, doing things faster implies that something is being sacrificed, for example accuracy. The sentence you posted says that the approximation is fast, but it does not suffer from reduced accuracy.

Fast and accurate would mean essentially the same thing, but the way it was phrased emphasizes that accuracy is not compromised, contrary to what might be expected.

  • 1
    I wonder if this sentence wouldn't be clearer with an and. Especially because non english speaker might not be aware of the second meaning of but. And especially because there is such a contrast non english speaker might think there is a not missing.
    – Hakaishin
    Jun 5, 2018 at 13:22
  • 3
    @Hakaishin: Anglophones write/speak English with the intention that other Anglophones should understand them - they're not normally interested in how easily they might be understood by non-native speakers. It's possible to use the conjunction and rather than but in your cited context, but this would slightly shift the nuance. Trust me - the writer knows what he's doing. Jun 5, 2018 at 13:31

Normally there is a trade-off when doing something fast, which involves cutting corners and thus reducing accuracy. In this sentence, the claim is made that despite being fast, it is still accurate.

The use of approximation already implies a lack of accuracy, so with but this implication is acknowledged. The difference to fast and accurate is that it presumes the trade-off, and emphasise that it is not a mistake (ie there is no missing not).


But has the same literal meaning as and. It has also a presupposition of surprise -- the speaker acknowledges a reasonable expectation of a possible different result.

So, while saying fast and accurate just means 'fast and accurate',
saying fast but accurate means 'fast and -- surprisingly -- accurate'.

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