Не мог бы ты одолжить мне свою книгу до завтра?

the book

Breakdown of Не мог бы ты одолжить мне свою книгу до завтра?

• не: not
• мне: me
• завтра: tomorrow

Questions & Answers about Не мог бы ты одолжить мне свою книгу до завтра?

Why does the sentence begin with не if the speaker is making a request, not saying something negative?

Because Не мог бы ты... ? is a standard polite way to make a request in Russian.

Literally, it is close to Couldn’t you...? or Wouldn’t you be able to...? In both Russian and English, this kind of negative wording can sound softer and less direct than a plain command.

Compare:

• Одолжи мне книгу. — Lend me the book. (direct)
• Можешь одолжить мне книгу? — Can you lend me the book? (neutral)
• Не мог бы ты одолжить мне книгу? — Could you lend me the book? (more polite / softer)

So the не does not make the whole meaning negative in practice; it softens the request.

Why is мог in the past tense? Doesn’t that literally mean could in the past?

On its own, yes, мог is the past tense of мочь (to be able to). But in Russian, the combination past tense + бы is a common way to express the conditional mood.

So:

• мог = could / was able
• мог бы = could / would be able to

That is why Не мог бы ты... ? means Could you...? rather than something strictly about the past.

This is one of the most common polite request patterns in Russian.

What exactly does do here?