[majid72]

Hello
Could someone please explain to me the difference between by and until in negative statements like these ones?

A- I didn't get up by nine o'clock.
B- I didn't get up until nine o'clock.

C- He won't be back by Friday.
D- He won't be back until Friday.

E- They won't publish my book by March.
F- They won't publish my book until March.

G- I won't work by the age of 30.
H- I won't work until the age of 30.

Thanks a lot.

[alawton]

When you use "by" in sentences like "He won't be back by Friday." or "They won't publish my book by March" you are saying the desired event could occur any time after the specified time. In these same examples, if you replace "by" with "until" you are saying that he will be back no earlier than Friday, or the book will be published no earlier than March. In using "until" you are being specific on exactly when the even will occur. Tell me if this makes sense or not.

[majid72]

Thank you very much alawton for your great and clear answer.