# By vs. Until

'By' and 'until' are both used to talk about time but there are differences between them. In this lesson, we will learn more about their uses and differences.

## What Is Their Main Difference?

The main difference between 'by' and 'until' is that 'by' talks about deadline while 'until' refers to all the time between the action's starting point to the end of the action.

We use 'by' to talk only about the deadline. When we use 'by' we are emphasizing the time that an action or event came to an end. Have a look:

Your assignments must be on my desk by Wednesday.

I need to be home by 9 p.m.

## Talking about a Period of Time

We use 'until' to talk about the time between a starting point and the end of the time period. For example:

I have to work until 4 p.m.

The Zoo is only open until sunset.

## With Other Prepositions

'Until' can be used with other prepositions to give more detail about the time period. Have a look:

Our work days are from 9 a.m. until 6 p.m.

The ice festival is open from December until February.

## Are They Interchangeable?

'By' and 'until' are not interchangeable. Replacing them with each other will completely change the meaning of the sentence.

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