By vs Until / Till
We use by to talk about a deadline when something will happen before that time.
By next week
By six o'clock
I'll be back by 7 o'clock.
The deadline is 7 o'clock so I promise to be back anytime before 7, latest at 6:59.
I'll have gotten my degree in English by next year.
I expect to / promise to get my degree at a time between now and next year. In other words, I will be able to say I have my English degree when the next year comes.
Until / Till
Until and till are the same and interchangeable. Until a newer word and is usually preferred over till in writing and in speech. We use until
to talk about something that will keep going on for a duration of time from a specific time to another.
Alan came yesterday. He will stay with us until the weekend.
Alan is with us at the moment and he is going to stay with us during the time from now to weekend.Sometimes we can use both by and until in a sentence but their meanings differ from one another.
He has bad fever. He needs to be in bed until 10 o'clock.
He is already in bed and he needs to stay in bed.
He has bad fever. He needs to be in bed by 10 o'clock.
He is not in bed but for his goodness he needs to go to bed latest at 10 o'clock.
Quick ExerciseChoose by or until.