By vs Until: Difference and Comparison

We are now going to look at the terms “by” and “until.” These two words are used so commonly in the English language and it is so critical to know the difference between these two.

Key Takeaways

  1. “By” indicates a deadline or the end of a period in which an action should be completed, while “until” denotes the duration or continuation of a step up to a specific point in time.
  2. Using “by” in a sentence implies an action will be finished before or at a specified time, while using “until” suggests the movement will continue and then stop at that time.
  3. These words can create ambiguity if used interchangeably, describing different relationships between actions and time.

By vs Until

By is used when referring to ending or accomplishing something before a particular time or deadline. Until tell about the time span or duration leading up to a certain specific point or event.

By vs Until

Comparison Table

Parameter of ComparisonByUntil
Meaning“Not later than”“Up to a specific time or event.”
Kind of SpeechPreposition, Adverb, NounPreposition, Conjunction
Specific TimeAssociated with a specific timeNot associated with a specific time
ExamplesClarence will be back in town by Monday. Roger will be at the wedding by ten o’clock.Mary Ann will be out of town until Friday. Jamal will not be at the wedding until ten o’clock.

What is “by”?

In order to fully understand just what the word “by” is, we first of all need to get a working definition of this word. According to Merriam-Webster, the word “by” is defined as “not later than.”

Moreover, the sample sentence that Merriam-Webster gives out is something like this: “Todd will be there by 4 p.m.”


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Naturally, this sentence could easily be rewritten to “Todd will be there not later than 4 p.m.” Simply put, this is when Todd is expected to be there.


What is “Until”?

Of course, the word “Until” is a little bit different than “By.”. This word is often used as either a preposition or as a conjunction.

As a preposition, “until” is utilized as a word to establish some type of continuance. One sample sentence would be this: “He stayed at the office until that evening.

Interestingly enough, the word “until” has had a long and quirky history. Some variation of the word has been around since at least the 13th century.

Moreover, there are many different variations of the word, including such examples as “till” or “’til.” Naturally, one would think that these examples are a newer version of “until”, but they would actually be wrong.

Believe it or not, “till” is an older version of the word “until.”

One of the main reasons why “until” has such a unique history would be because it is actually a newer version of the word “till” and not the other way around. “Till” didn’t start meaning the same as “until” until around the beginning of the 13th Century.

Of course, the modern variation of “until” would be “’til”, and this seems to have become increasingly popular in the 20th Century. Of course, there are some writers who believe that it was introduced as early as the 19th Century, and there is, indeed, some evidence for that belief.


Main Differences Between “By” and “Until”

Even though the words “by” and “until” are very similar, they are some main differences. Consider some of the following facts:

1) Completion of Deadline

The word “by” explains a specific deadline in a sentence. When you encounter “by” in a sentence, that means that it is explaining a certain deadline.

For example, take a look at this sentence: “We will make it to the picnic by 12 p.m.” In this case, the expected deadline for your arrival is 12 p.m.

“Until” refers to a deadline as well, but it is a bit vaguer. The word “until” is similar to “by”, but it is also quite a bit different.

Instead of completely referring to the deadline, “until” is more focused on the period leading up to the deadline.

2) Reference to Time

Unlike “by”, “until” is not followed by a specific point in time. When you see the word “by” in a sentence, it will generally go something like this: “by Wednesday”; “by tomorrow”; by next week; and so on.

This is because “by” is directed at a specific point in time.

On the other hand, “until” is quite a bit different than “by”. “Until” will be in sentences such as this one: “George will be out of town until Friday”. Thus, the word “until” is more concerned with when the situation will change.

3) Verb

The word “until” is best expressed with a verb that demonstrates continuity. In a nutshell, if the verb can be used in a continuous form, then it is better to use “until” in the sentence.

Here is an example: “Joseph was very tired, so he slept until noon.”

On the other hand, “by” will only refer to a verb that is just used once, at a fixed point in time. This is one of the main reasons why “by” will refer to deadlines.

Sample sentences of this would be “You have to finish by Thursday”, “You need to turn in the report by Sunday”, or “Please leave the pool by 4 p.m.”

Difference Between By and Until
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