Difference Between By and Until

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.

By vs Until

The main difference between By and Until is that ‘by’ refers to time or to imply someone for something whereas until means a situation that is continued and will end in the future at a particular time. By stands as a preposition, adverb, and noun while until stands as a preposition or conjunction in the part of speech.

By vs Until

Comparison Table Between By and Until

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.”

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One of the main reasons why “until” has such a unique history would be because it is actually a newer version of the word “till” and not the other way around.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 usually 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 usually 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 usually 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” usually 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 usually 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

Frequently Asked Questions (FAQ) About By and Until

Which tense is used with Until?

Until means up to the point of time or event that is being mentioned in the sentence. “‘Until” can be used with all the three tenses if we are talking about the entire sentence.
Examples –
They played cricket until Rohan arrived.
I am not doing anything until they have returned my book.
I will not go to the party until you come to my house to pick me.
Judging from the examples, until can be used in all the three sentences. However, there is a slight distinction when until is used in the future tense.
Will is not used after until even if the succeeding sentence is in the future tense. It is apparent in the third example as well. ‘Until you will come’ is grammatically incorrect and it must be ‘until you come’.

Can we use not with Until?

Not can be used with until. For instance, Not until he accepts his mistake, will I lend him my notes again.

What type of conjunction is Until?

Until is a type of subordinating conjunction. Subordinating conjunction used to join dependent clauses with independent clauses.
For example – I will not leave until my homework is done.

Is Until inclusive or exclusive?

It depends on the intention and tone of the speaker until can be both inclusive and exclusive.
If the situation defined in the sentence denotes the absence of the speaker, it is exclusive. It is inclusive when the situation defined in the sentence denotes the presence of the speaker.
Let’s look at these examples to understand it better.
Example – I’m not going to attend the classes until 22nd December 2019. In this sentence, it clearly states that ‘I’ usually attend classes but now I will not attend classes until a specific time.
It means as soon as that specific time starts I will start attending the classes as well. It marks the speaker’s absence in the time period here.
Example – I will be staying in Los Angeles until 26th December 2020. In this sentence, ‘I’ will continue to stay in Los Angeles until a specific date.
It means that the person will not be present in Los Angeles on the same date. It marks the speaker’s presence in the mentioned place until the time period ends.


There is no question that these two words are very similar. There also is no question that they both have found many different uses in the English language.

However, it is important to properly delineate between the two.

Reaching a full understanding of when to use these two terms will definitely go a long way in helping your English skills!

Key Differences Between By and Until (PDF Format)

Download the key differences in .PDF format, to read or print them later:

Difference Between By and Until


  1. https://dictionary.cambridge.org/dictionary/english/by
  2. https://www.merriam-webster.com/dictionary/until
  3. https://speakspeak.com/resources/english-grammar-rules/conjunctions/until
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