Difference between By and Until

Difference between By and Until

By and until can be easily confused. Prepositions are the words that precede a noun or a pronoun to show the relation or connect it to another element within the sentence. “By” is used to describe an action or event that happens on or before a particular moment. By and Until are the two prepositions of time, which are commonly misinterpreted. They are used differently and after a little studying, you should have no problems using them. However, the preposition ‘by‘ acts as a deadline in a sentence, indicating the time up to which something must be done or completed.

On the contrary, the word ‘until‘ focuses on the period, before the deadline. “Until” is used to describe a state or situation in a period of time up to a particular moment. You may think of “until” as referring to the moment a state or situation changes.
E.g. Comments on the draft may be submitted until (date).

Difference between By and Until


  • The word by means ‘not later than’, which indicates something must be achieved or completed.
  • Use “by” to talk about a deadline. When we use “by” we are only concerned about the deadline or the time when something or some period ends.
  • The preposition ‘by’ is used to express an event or action that should be happened on or before a definite moment of time.
  • The word ‘by’ with reference to time is used to set a time limit for an action to finish. This means that the action must be completed on or before the expiry of that time. Hence, it highlights a specific point in time or moment in the future, when that action should be finished or something has to be achieved.
  • ‘By’ is used when there is a specific time limit, for doing something, to indicate that something has to be achieved/completed by that particular time.
  • Examples: John will come back to the town by Monday. Kate will be at the party by 4’O clock


  • Until is used to show how long a state or situation continues, so it marks a point at which the situation or state is going to change.
  • We use “until” to talk about the period of time from a starting point until a deadline or the end of some period of time.
  • We use the word ‘until’ to describe a situation, action, or state which will change or stop, at a particular point in time.
  • The word ‘until’ describes an action, state, or situation which continues up to a long time, and then it stops or changes at a specific moment or point in time. Informally we use the word till, instead of until.
  • If the focus is not on the time limit but the period before the deadline, then we use until to show that something continues over a period of time and then stops once a particular point (mentioned) is reached.
  • Examples: John will be out of town until Monday. Kate will be at the party until 4’O clock.

“By” refers to a deadline. We usually use the verbs “must”, “need”, or “have” when we make sentences with “by”. We use “until” to refer to a period of time in which something happens or is possible. We usually use the words “can”, “will”, or any present tense verbs with “until”.