She knew he wouldn't open the doorโ€”but when he did/did so, she had to be prepared.

She looked at the alley. No matter how long she did/did so, he wouldn't show up.

Should it be did or did so in situations like these?

  • 1
    It can be either. "Did so" is slightly more formal. Feb 24, 2022 at 15:56

2 Answers 2


"Did" alone is more casual, but it is also much more common because neither "did" nor "did so" are great options for a formal situation.

In an essay or other formal document I would expect

She knew he would not open the door, but she still had to be prepared.


Regardless of the time she spent looking at the alley, He was not going to show up.

I prefer speaking, hearing, writing and reading "did" over "did so" every time, and that seems to be the general consensus in AmE here in the US.


Both are correct.

๐——๐—ผ, ๐—ฑ๐—ผ ๐—ถ๐˜, and ๐—ฑ๐—ผ ๐˜๐—ต๐—ฎ๐˜ can be used to avoid repeating a main verb and its object or complement.

He did- He opened the door.

He did so- He opened the door.

She did- She looked at...

She did so- She looked at...

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