In English, we often use a pair of interrogative pronouns – in this specific instance, "which" and "what" – to express the idea of:

Which antibiotic works best against what type of infection – you need to have that knowledge under your belt.

German and Russian also uses the combination of two interrogative pronouns, "welche & welche" and "какой & какой", respectively in an instance like this.

On the other hand, I just realised that this "which & what" perhaps might not translate well into French as "quel & quel":

{???}: Quel antibiotique sera plus efficace contre quel type d'infection : voilà ce qu'il te faut connaître.

I wonder if it sounds more idiomatic to say:

Quel antibiotique sera plus efficace contre tel type d'infection : voilà ce qu'il te faut connaître.

  • 3
    In English it's usually which/which or, more colloquially, what/what. Not sure I've ever heard which/what, but if I did I'd regard it as the same sort of accidental conflation seen in a phrase that one friend keeps saying: "at the same token"... But asking about the underlying structure in French seems valid in any case.
    – Luke Sawczak
    Jul 4, 2018 at 13:14
  • @LukeSawczak The following two both sound odd to my ears: "Which antibiotic works best against which type of infection" and "What antibiotic works best against what type of infection". I think that the interrogative pronoun "which" usually applies to a narrower range of choices than "what" indicates. Here the number of types of infections that I have in mind is quite large, so "what type of infection" seems a better fit. And then, we go on to consider which antibiotic we should choose from several different (rather limited) options against a given infection. Jul 4, 2018 at 13:59
  • @LukeSawczak But of course, in an instance like "I can't tell which is which", the two "which"s are the choice by default. Anyway, that's an interesting point you've raised there. I'm hoping that other English speakers chime in with their thoughts? Jul 4, 2018 at 14:16
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    What can I say? Those two that sound odd to you are, in my grammar, the acceptable ones. It's worth noting that using "what" as a synonym for "which", as one does in "what type of infection", is colloquial anyway — so it would be odd if the only standard version required it!
    – Luke Sawczak
    Jul 4, 2018 at 14:18

2 Answers 2


Les deux phrases en français sont correctes mais n'ont pas la même signification. Tel réfère à une partie des infections alors que quel n'en détermine aucune en particulier. On pourrait remplacer Quel antibiotique sera plus efficace contre tel type d'infection par Quel antibiotique sera plus efficace contre ce/ces type d'infection. La première forme avec quel et quel me paraît donc la meilleure traduction.


It is idiomatic to say

Quel X pour quel Y

For example it would be fine to say:

Quel antibiotique pour quel type d'infection : ...

It's also possible to say something like:

Quel antibiotique fonctionne le mieux contre quel type d'infection : ...

However, personally I find this second construction quite heavy; maybe too many words between the two quels?

Finally the following also works:

Tel antibiotique pour telle infection : ...

...which corresponds to the English "such antibiotic for such infection", i.e. it implicitly invokes a random example rather than a choice.

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