"By" and "Until": What's the Difference?

Both "by" and "until" are prepositions that focus on time. But many English learners struggle to understand what makes them different, so they often use one when the other is more appropriate. 

We're here to help! This article will explain their differences and give examples of how each can be used.

By

"By" is used when the focus is on a deadline or a specific point at which something must be done or completed. It's always followed by a time or event.

• I have to finish this project by Friday morning.
• They should arrive by 5pm.
• He should have gotten here by now.
• The package should be delivered by the end of next week.
• You must complete the test by the time the alarm sounds.

In each of these examples, the end of the period of time is the most important thing.

Until

With "until," the end is not the focus; instead it is the complete period of time, including the beginning, middle and end.

• I have until Friday morning to finish this project.

In this example, the speaker is referring to all of the time they have, which starts from now and continues to Friday morning.

• It took until 5pm for them to arrive.

Here, the speaker is referencing the total amount of time that was required for someone to make a journey.

• The package was in transit until this evening.
• How much longer until we arrive?
• You have until when the alarm sounds to complete the test.
• Until now, I thought "by" and "until" were used the same way!

In these examples, the total period of time is important, not just the end, so only "until" is correct to use.

Yet

Let's look at one more word that's related to the previous two we've discussed. 

"Yet" is similar to "until" because it also refers to a period of time. However, the important difference is that the period is not finished. 

"Yet" is mostly used in questions and negative sentences, as in the following examples:

• Are you finished yet?
• Because of problems with our supplier, we haven't completed production yet.
• We're delaying the start of the meeting because the team leader hasn't arrived yet.

Wrap-up

In summary, "by" refers to a deadline or an endpoint, while "until" focuses on a total period of time. Meanwhile, "yet" refers to something that is not complete.

If you're ever confused about which one to use, just think about which of these ideas is most important for what you want to say. You can always come back to this article if you need to be reminded! 💡

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