Learn Hardcore Chinese: wǒ de shū bèi tā jiè zǒu le, búguò míngtiān tā huì sòng huílái. - My book was borrowed by him, but he will bring it back tomorrow.

被 marks passive voice. The affected thing comes first (here 我的书), the agent follows 被 (here 他), then the verb: 书被他借走了 = “The book was borrowed by him.” Active equivalent: 他借走了我的书。

Does 被 always imply something negative or unwanted?

Not always. It often suggests an event outside the subject’s control and can sound slightly adverse, but it can be neutral depending on context. Here it’s close to “was borrowed (away).” If you want a neutral active tone, say 他借走了我的书 or 他把我的书借走了.

How can I say this without 被?

Common options:

他把我的书借走了。
他借走了我的书。 Informal colloquial passive: 我的书给他借走了。 (using 给 as a passive marker)

What does the 走 in 借走 add?

走 is a resultative complement meaning “away.” 借了 = borrowed (no emphasis on where it is now); 借走了 = borrowed and took it away (it’s gone from here). Similar patterns: 拿走、带走、买走.

Can I use 借去 instead of 借走?

Yes. 借去 also means “borrow and take away.” 走 is very common and colloquial; 去 can feel a bit more written. Both are fine here.

What does 了 do in 借走了?

It’s the perfective aspect marker: the borrowing event is completed. It doesn’t inherently mean “past”; time comes from context. Without 了, 书被他借走 is usually felt incomplete/unidiomatic.

What’s the difference between verb 了 and sentence-final 了? Could I add another 了 at the end?

Verb 了 (after the verb/complement) marks completion (here after 走).
Sentence-final 了 indicates a new situation/change. Here verb 了 is enough: 书被他借走了。 Adding a sentence-final 了 would be unnecessary.

Why use 不过 instead of 但是/可是?

All mean “but.” 不过 is a bit softer and very common in speech. 但是/可是 are also fine: ……不过/但是/可是明天他会送回来。

What does 会 mean here? Could I use 要?

Here 会 expresses a likely/expected future: “will.” Alternatives:

要: stronger sense of plan/intention: 明天他要送回来。
Bare future in casual speech: 明天他送回来。

Why say 送回来 instead of 还(给我)?

还 = return to the owner; specify the person with 还给我.
送回来 emphasizes physically bringing/sending it back to where the speaker is. So use 明天他会还给我 to stress giving back to you; 明天他会把书送回来 to stress delivering it here.

How do 来 and 去 work in 回来/回去?

They show direction relative to the speaker:

回来: back toward here.
回去: back toward there. So 送回来 if he brings it back to you/your place; 送回去 if he returns it to another place.

Can I omit the second 他?

Yes, if it’s clear from context: ……不过明天会送回来。 Chinese often omits repeated subjects when unambiguous.

Where can I put 明天?

Both are natural:

明天他会送回来。
他明天会送回来。 Time phrases typically appear before the verb phrase, either sentence-initially or right after the subject.

Why 我的书 and not 我书?

Ordinary nouns need the possessive marker 的: 我的书. Dropping 的 is common mainly with close kin terms or set phrases (e.g., 我妈、我们家), not with 书.

Does 书 mean one book or several here?

Unspecified. To be precise:

One: 我的那本书被他借走了。
Some: 我的一些书被他借走了。
All: 我的书都被他借走了。 Measure word for books: 本.

Does 借 mean “borrow” or “lend”? How do I say each?

借 can be either; patterns disambiguate:

Borrow from: 跟/向 + 人 + 借 (e.g., 他跟我借了一本书。)
Lend to: 借给 + 人 (e.g., 我借给他一本书。) In 书被他借走了, “he” is the borrower.

Can 给 mark passive here?

In colloquial speech, yes: 我的书给他借走了。 You may also hear 让/叫: 我的书让他借走了。 These are informal; 被 is the standard passive marker.

How do I negate the first clause?

Use 没/没有 and drop 了:

我的书没(有)被他借走。 Active negative: 他没(有)借走我的书。

How do I ask “Who borrowed my book?” with this structure?

Passive focus: 我的书被谁借走了？
Active/把: 谁把我的书借走了？

If I want to mention the object again in the second clause, how do I say it?

Add 把 or a pronoun:

不过明天他会把书送回来。
不过明天他会把它送回来。 (它 refers to the book.)

Difference between 送回来、拿回来、带回来?

送回来: deliver/bring back for someone else (emphasizes delivering).
拿回来: take/carry back (hand-carry).
带回来: bring back along (accompaniment). All are possible; choose based on nuance and how the book returns.