Confusable words

until vs by: what's the difference?

until
preposition
vs
by
preposition
? ?

Until and by both point to a moment in the future, but one describes something continuing and the other describes a deadline.

Until

preposition

Until describes an action that continues up to a certain point, then stops.

  • I'll be at work until 6pm.
  • Wait here until I come back.

By

preposition

By describes a deadline, the latest possible moment something happens.

  • Please finish the report by Friday.
  • I need to be home by 6pm.

Side by side

until by
Describes An action continuing up to a point A deadline, the latest moment
Typical verbs stay, wait, work, continue finish, submit, arrive, complete
Simple test "until 6pm" means continuing up to 6pm "by 6pm" means no later than 6pm

Quick rule

Until means continuing up to a point. By means no later than a point. "I'll wait until 6" but "finish it by 6."

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