daehageseo mannan seonbaega nae jeongong chaegeul billyeojwosseo.

In Korean, a verb can go directly before a noun to describe it. This is like a relative clause in English.

• 만난 선배 = the senior / upperclassman that I met
• The verb 만나다 (to meet) becomes 만난 to modify the noun.

So:

• 대학에서 만난 선배 = the senior I met at university

This structure is extremely common in Korean:

• 어제 본 영화 = the movie I saw yesterday
• 제가 읽은 책 = the book I read

Because it describes a completed action: the meeting already happened.

• 만난 선배 does not mean the whole sentence is in past because of that form.
• It means the senior whom I met.

The main verb of the sentence is 빌려줬어, and that is also in the past tense, so the full sentence describes a past event: someone lent the speaker a book.

Here, 대학에서 means at university / in college as the place where the meeting happened.

Korean often uses:

• 에 for location/existence/destination
• 에서 for the place where an action happens

Since 만나다 is an action, 에서 is natural:

• 대학에서 만난 선배 = the senior I met at university

Compare:

• 학교에 있어 = I am at school
• 학교에서 공부해 = I study at school

선배 is a very common Korean social term. It refers to someone who entered a school, company, or field earlier than you, or someone more senior in that shared environment.

In this sentence, it most naturally means:

• an upperclassman
• a senior at university
• or more broadly a senior person I know from university

It is not exactly the same as the English word senior in every context, because Korean uses 선배 as an important relationship term.

The opposite word is:

• 후배 = junior

Both can be possible in different contexts, but 가 here marks 선배 as the subject in a straightforward way.

• 선배가 내 전공 책을 빌려줬어 = It was the senior who lent me my major book / A senior lent me my major book

Using 는 would add more of a topic or contrast nuance:

• 선배는 내 전공 책을 빌려줬어 could sound more like As for the senior, they lent me my major book or contrast with someone else.

In isolated example sentences, 가 is often the most neutral choice for introducing the subject of the action.

내 is the common shortened form of 나의, which means my.

So:

• 내 전공 책 = my major book
• 나의 전공 책 means the same thing, but sounds more formal, written, or emphatic

In everyday speech, Koreans usually prefer the shorter forms:

• 내 = my
• 네 = your
  though in speech 네 is often pronounced more like 니 to avoid confusion with 내

Literally, it is major book or book for my major.

In natural English, this could mean:

• a textbook for my major
• a book related to my field of study
• one of my course books

Korean often puts nouns together like this:

• 전공 = major / field of study
• 책 = book

So 전공 책 is a noun phrase where the first noun describes the second.

Depending on context, it may sound a little more natural in English as a textbook for my major rather than the very literal my major book.

It is implied in the verb 빌려줬어.

The verb 빌려주다 means to lend or more literally to give for someone to borrow. The person receiving the favor is often understood from context and can be omitted if obvious.

So:

• 내 전공 책을 빌려줬어 = lent me my major book or lent my major book to me

If you wanted to state me explicitly, you could say:

• 내게 전공 책을 빌려줬어
• 나한테 전공 책을 빌려줬어

Both mean lent me a book for my major.

This is a very common point of confusion.

• 빌리다 = to borrow
• 빌려주다 = to lend

So:

• 나는 책을 빌렸어 = I borrowed a book
• 선배가 책을 빌려줬어 = The senior lent me a book

A helpful way to remember it:

• 빌리다 = from the borrower’s point of view
• 빌려주다 = from the lender’s point of view

In your sentence, the senior is the one doing the lending, so 빌려줬어 is correct.

빌려줬어 is a contracted spoken form.

It comes from:

• 빌려 주었어

And that breaks down into:

• 빌려 from 빌리다
• 주다 = to give, often adding the sense of doing something for someone
• -었어 = past tense informal ending

So 빌려주었어 became 빌려줬어 in natural speech.

This ending is:

• casual
• informal
• appropriate with friends, younger people, or in relaxed conversation

A more polite version would be:

• 빌려줬어요

Because Korean is a verb-final language. The main verb usually comes at the end, and everything else builds up before it.

In this sentence:

• 대학에서 만난 = describes the senior
• 선배가 = subject
• 내 전공 책을 = object
• 빌려줬어 = final verb

So Korean often feels like you have to wait until the end to get the full action. This is normal.

A good way to read it is in chunks:

• 대학에서 만난 → whom I met at university
• 선배가 → the senior
• 내 전공 책을 → my major book
• 빌려줬어 → lent (to me)

That chunking approach makes long Korean sentences much easier to understand.