I have seen sentence structures like the following:

Once opened, the chicken broth is good for 2 days.

My two questions:

  1. what tense should be used after once? past, or the past participle? So, which one is correct:

    Once drunk, the bottle should be disposed of properly.


    Once drank, the bottle should be disposed of properly.


  1. Can such a sentence structure be used in formal contexts?
  • There is an error in your sentences that unintentionally makes them very funny. The original sentence is about the chicken broth: "Once opened, the chicken broth..." but your sentences are about you: "Once drunk, you..." This actually says that once you are drunk, you should dispose of the bottle! A more accurate phrasing would be "Once drunk, the bottle should (etc.)" But don't worry; even many native speakers make this kind of mistake.
    – stangdon
    Sep 20, 2018 at 16:52
  • @stangdon Haha, this was actually pretty funny, too bad that it's fixed now and the future readers will be deprived of a good laugh :)
    – narengi
    Sep 20, 2018 at 16:58
  • It's still there.
    – Lambie
    Sep 20, 2018 at 17:46

1 Answer 1


The words "opened" and "drunk" here are functioning like adjectives; they describe the state of the broth/bottle. For this purpose, use the past participle. It's the same as in the sentence:

That seat was taken.

And yes, this structure is OK to use in formal contexts.

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