ESEN
Which one to use?Intermediateprepositionpreposition
ByvsUntil
"By" indicates a deadline (no later than); "until" indicates continuous duration up to a point.
Side-by-side comparison
By
preposition"By" sets a deadline: the action must happen at some point up to and including that moment. "By 5 pm" = no later than 5 pm. It does not mean the action continues all the way up to that point.
Please send me the report by Friday.
The package should arrive by next Tuesday.
You need to finish this by noon.
Until
preposition"Until" means an action or state continues without interruption up to a specific point. "I will wait until 5 pm" = I will be waiting continuously all the way up to 5 pm. It implies duration, not just a deadline.
She worked until midnight to finish the project.
The store is open until nine at night.
Wait until I get back before starting dinner.
Common mistake
- •"The store is open by 9pm" is wrong when meaning it closes at 9.
- •Continuity up to that point uses "until": "The store is open until 9pm".
- •"By 9pm" would mean something must happen before 9, not that something continues up to that time.
Trick to remember it
- •"By" = deadline (something must happen before that time).
- •"Until" = duration (the action continues up to that point).
- •"Finish by 5" = before 5.
- •"Work until 5" = continuously until 5.
Quick rule
- •"By" = no later than (deadline).
- •"Until" = up to (continuous duration).
Did you know?
"Till" is an informal synonym of "until" and is completely correct: "wait till I get back." Very common in colloquial American English. "By now" (already, at this point) is an idiomatic expression: "You should know this by now." "By then" = by that time: "We should be done by then." All these expressions use "by" with no confusion with "until".
Practise what you learned
Exercise 1 · Pick the right one
The café is open _____ midnight. You have plenty of time.
Exercise 2 · Pick the right one
You need to hand in your homework _____ tomorrow.
Exercise 3 · Form the word
Related word pairs
DuringvsWhile
One is followed by a noun, the other is followed by a full clause.
SincevsFor
"Since" marks the specific point when something started; "for" indicates how long something has lasted.
StillvsYet
"Still" means something continues to happen; "yet" means something has not happened but is expected.
AvsAn
'A' is used before consonant sounds; 'an' is used before vowel sounds.
Bryan López
Founder of SpeakUP Academy