Hi guys! This is Kee from BBC Learning English,
and today I'm going to tell you the differences
between 'until' and 'by'.
We use 'until' to talk about doing something
up to a certain point in time.
If I say:
I have to take care of my dog until 5pm,
it means I will start taking care of my dog now
and stop taking care of it at 5pm.
On the other hand,
we use 'by' to talk about doing something
before a future time or deadline.
If I say:
I have to finish an essay by 5pm,
it means I can start any time
but I will make sure that at 5pm
I have finished writing the essay.
So, I may even finish it at 3pm or any time before 5.
So we use 'until' to describe doing something
up to a certain point in time
and we use 'by' to describe doing something
before a future time or deadline.