Meaning of "by Sunday"

[Tung Quoc]

Dear teachers,

Please read:

I should have finished the book by Sunday.

1. What does "by" mean?
2.What is the meaning of “by Sunday”?

Thanks
Quoc

[Alan]

Hi,

By has the notion of not later than or before. By Sunday means not later than/before Sunday.

Alan
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English as a Second Language
You can read my ESL story Present Simple