Grammar dilemmas: “until” or “by”?

An interesting question came up in a recent conversation class with a student. It had to do with the use of the words “until” and “by”, both of which are translated the same in the student’s mother tongue. 

At first glance, both do seem to refer to the same thing — a point up to which something lasts or when an action ends. Be careful, though: while similar, in English they are definitely not the same! 

In this post I’ll briefly explain the difference, illustrating it with a few examples. As always, there‘s also an online grammar quiz waiting for you.

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UNTIL

One of several uses of the word “until” is that of a preposition of time (it can also be a conjunction, but that’s a separate topic). It’s followed by a noun or a time reference:

Yesterday I had to work until 7pm. 

I’ll be out of office until Tuesday.

In both sentences, the action continues up to a certain point and then stops.

EXTRA INFO

#1 You can shorten the word until to till or ‘til, but avoid this in formal writing as it sounds informal. Grammatically, however, they are all exactly the same.

#2 Until is not used to talk about quantity or distance.

• For distance, use as far as: From my house I can see as far as the mountains. 
• For quantity, use up to: My fridge can store up to twenty cans of beer.

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BY

“By” gives us the deadline by which (i.e. before) something needs to happen. The action doesn’t continue until that time — it just has to finish at any point by that time.

She usually arrives to work by 9am. (i.e. at some point before 9)

Please finish your homework by tomorrow. (i.e. at any point between now and the tomorrow’s lesson)

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I think you’re ready now for a quick grammar quiz. If you have any further questions about this topic, do post them in the comments section below!

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NOTES