The difference between “by” and “until”

WRONG
Write the report until 5 pm.
RIGHT
Write the report by 5 pm. 

Write the report until 5 pm means “Start writing the report now, continue writing it until 5 pm, then stop writing it regardless of whether it is finished or not.”

Write the report by 5 pm means “Make sure that at 5 pm the report is written and finished”.

As a preposition of time “by” means “on or before”.
E.g. We will send you the documents by Friday.

  • Use “by” when you refer to a deadline.

“Until” means “up to a particular time”.
E.g. We have until Friday to send out the documents.

  • Use “until” when you refer to the period of time before a deadline.

“By” is used to describe an action or event that happens on or before a particular moment.
E.g. We expect to know the judgment by the end of November.

“Until” is used to describe a state or situation in the period of time up to a particular moment.
E.g. The court proceedings are expected to last until November.

You may think of “until” as referring to the moment a state or situation changes.
E.g. Comments on the draft may be submitted until 30 April 2012.

Here’s a summary:

1.         I can do it by 5 pm.
            Now   → do it and finish it →   5 pm (it will be finished)

2.         I can do it until 5 pm.
            Now   →       do it       →   5 pm (I’ll stop even if I haven’t finished)

3.         I can’t do it by 5 pm.
            Now   → do it / not do it →   5 pm (either way it won’t be finished)

4.         I can’t do it until 5 pm.
            Now   →  can’t do it  →   5 pm (I’ll start)

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13 Responses to The difference between “by” and “until”

  1. Boram LEE says:

    Thanks for your very kind explain!!

  2. Je vɑis vous dire que ce n’est pas incohérent ..

  3. There is definately a great deal to find out about
    this topic. I really like all the points you made.

  4. jy says:

    This was super helpful. Thank you so much.

  5. didaanastasi says:

    Incredibly helpful and easy to comprehend! Thanks a lot !

  6. Sueli Fernandes Martins says:

    Thanks a lot! Muito obrigada pela explicação!

  7. Mohammad Javaid says:

    Thank you very much for giving me such good information.

  8. Pingback: By vs. Until | worddive

  9. ahn says:

    easy explanation thank you for teaching

  10. Lenka says:

    thanks! very helpful

  11. Ann1412 says:

    what’s the difference between “on” and “by”? ex. the manager said he would return to the company …. 2 PM. (is it “by” or “on”)?

    • You use “on” to refer to a day or date – e.g. “The manager said he would return to the company on 15 September” or “”The manager said he would return to the company on Friday”. You use “at” to refer to a time – e.g. “The manager said he would return to the company at 2 pm”. There’s a difference between “at” and “by”. “At” means at exactly that time; “by” means before or at that time, but not later.

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