As the owls flooded into the Great Hall as usual, everyone's attention was caught at once by a long, thin package carried by six large screech owls.

A thousand live bats fluttered from the walls and ceiling while a thousand more swooped over the tables in low black clouds, making the candles in the pumpkins stutter. (Harry Potter book1)

In the examples, what’s the difference between ‘as’ and ‘while’? Can each be changed with each other?

  • 4
    In these two contexts there's no difference in meaning, and they can reasonably be swapped. I think there's actually a good argument for doing so in the first example, to avoid the slightly jarring clash with "as usual", where "as" performs a different function. Jan 2, 2013 at 13:59
  • 2
    I agree. The only thing to add is that as can have causative as well as temporal meaning, so that in some contexts care needs to be taken in its use. Jan 2, 2013 at 15:26

1 Answer 1


I believe there is a slight connotative difference, in addition to the causative meaning of "as".

  • The word "while" implies that there are two comparable events taking place (in terms of duration) — there are a thousand bats fluttering and a thousand bats swooping over the same length of time.
  • The word "as" often refers to a specific temporal instance occurring within the confines of a larger duration of time — the owls flew in the room over a length of time, but everyone's attention was caught at once.

Generally speaking, they are interchangeable, but the reader will get a slightly different idea of when the events took place in comparison to each other.

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