what do you think you are playing at, walking off into the forest with Viktor Krum? I want you to swear, by return owl, that you are not going to go walking with anyone else at night. There is somebody highly dangerous at Hogwarts.

I'm wondering if we should add an article in "by return owl", like "by a return owl". Why does it not take any articles here? How should we understand it?

Excerpted from Harry Potter

  • "How are you getting to work?" "By car." Dec 27, 2018 at 4:51
  • @JasonBassford, Can it be "By red car"?
    – dan
    Dec 27, 2018 at 4:54
  • It would be extremely unusual to hear that. Dec 27, 2018 at 6:26
  • 1
    If I remember correctly, this excerpt is from a letter to Harry by Sirius. Maybe Sirius is just referring to the fact that Harry should send the response by the same owl that got him the letter in the first place, but then the definite article "the" makes more sense.
    – CinCout
    Dec 27, 2018 at 7:10
  • 1
    "Return post" did exist. At one time it was common for the postman to collect post at the same time as receiving it. In London there were five or six deliveries a day, and it would be reasonable for the wealthy to receive a postcard, ask the postman to wait, write respond to it, hand the response back to the postie for delivery the same day. This was called replying "by return post"
    – James K
    Dec 27, 2018 at 9:46

2 Answers 2


Here "owl" is being used in a rather unusual way. It is the uncountable method of delivering a letter.

When a word is used to give a method, it is used uncountably, even if the word would normally be countable:

Write your name in pencil (not in a pencil)
I came by bike (not by a bike)
Send it by return post (not a return post)

Similarly, when the method is "owl" you say "by return owl". And the original letter was delivered "by owl" too.


In the HP world, Wizard mail is via Owl Post. Thus, 30 years ago you might have said something like, "Drop the hotel keys in the return mail". In this case, because they're wizards, substitute "mail" for "Owl".

That's because "I want you to swear, by return owl, that you are not going to go walking with anyone else at night" means that they are swearing on the trustworthiness of Owl Post.

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