By vs. Until: What’s the Difference?2025.03.09

English learners often confuse “by” and “until” because both relate to time. However, they have different meanings.

“By” – A Deadline

Use “by” when something happens before or at a specific time.

Example: I need to finish my homework by 8 PM. (I will finish before or at 8 PM.)

Example: She must submit the report by Friday. (The latest time is Friday.)

“Until” – A Duration

Use “until” to show that something continues up to a specific time.

Example: I will study until 8 PM. (I will stop studying at 8 PM.)

Example: The store is open until midnight. (It stays open and then closes at midnight.)

Key Difference

Use “By” if you want to talk about the deadline (when something must be done).

Use “Until” if it is about the duration (how long something happens).

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