by
US /baɪ/
UK /baɪ/

1.
indicating the means of achieving something
:
•
He traveled by train.
•
She learned English by watching movies.
2.
indicating the agent performing an action in a passive sentence
:
•
The book was written by a famous author.
•
The ball was hit by the player.
3.
4.
indicating a deadline or a point in time before which something happens
:
•
Please submit your report by Friday.
•
I need to finish this by noon.