No puedo sacar otro libro porque se me olvidó el carné de la biblioteca.

In Spain, sacar un libro de la biblioteca commonly means to check out / borrow a book from the library.

So in this sentence, sacar otro libro is not just physically taking a book off a shelf. It means borrowing another book officially.

A few useful comparisons:

• sacar un libro de la biblioteca = to borrow/check out a library book
• prestar = to lend
  
  • La biblioteca presta libros = The library lends books
• devolver = to return

So from the speaker’s point of view, sacar is very natural in Spain for library use.

Because otro normally does not take un or una before it in Spanish.

So:

• otro libro = another book
• otra mesa = another table

Not:

• un otro libro ❌

This is a very common rule. Otro already carries the idea of another / one more, so Spanish does not usually add the indefinite article before it.

Se me olvidó is a very common Spanish way to say I forgot something, but literally it works more like:

• It slipped my mind
• It got forgotten on me

Spanish often uses this structure when something is presented as happening to the speaker, rather than as a deliberate action.

Breakdown:

• se = part of the construction
• me = to me / on me
• olvidó = was forgotten / slipped the mind
• el carné = the thing forgotten

So:

• Se me olvidó el carné = I forgot my library card / My library card slipped my mind

You can also say:

• Olvidé el carné

That is also correct, but se me olvidó el carné sounds very natural and often a bit less direct, more like I ended up forgetting it.

They do different jobs.

• me shows the person affected: to me / on me
• se is part of the idiomatic structure used with olvidar in this kind of sentence

This pattern is very common in Spanish:

• Se me perdió la llave = I lost the key / The key got lost on me
• Se te cayó el móvil = You dropped your phone
• Se nos olvidaron las entradas = We forgot the tickets

It often makes the event sound less intentional or more accidental.

Because the verb agrees with the thing forgotten, and here that thing is singular:

• el carné = singular

So:

• Se me olvidó el carné = singular verb

If the forgotten thing were plural, the verb would be plural too:

• Se me olvidaron las llaves = I forgot the keys

This is important because in this structure, the grammatical subject is not I. It is el carné.

Yes. In Spain, carné commonly means a card, especially an official or membership card, such as:

• carné de identidad = ID card
• carné de conducir = driving licence
• carné de la biblioteca = library card

It is masculine:

• el carné

In many other Spanish-speaking places, people may say la tarjeta de la biblioteca instead. But carné is very normal in Spain.

Both are possible.

• el carné de la biblioteca = the library card
• mi carné = my card

The sentence uses el carné de la biblioteca to be more specific. It makes clear which card the speaker forgot.

In Spanish, it is also very common to use the definite article where English would often prefer a possessive:

• Me duele la cabeza = My head hurts
• Se me olvidó el carné = I forgot my card

So el is perfectly natural here.

It describes carné.

So the meaning is:

• el carné de la biblioteca = the library card

Not:

• otro libro de la biblioteca = another book from the library

Even though the whole sentence is about books and a library, grammatically de la biblioteca is attached to carné here.

Because porque here is a conjunction meaning because.

• porque = because
• por qué = why

Examples:

• No voy porque estoy cansado. = I’m not going because I’m tired.
• ¿Por qué no vas? = Why aren’t you going?

So in your sentence, porque introduces the reason.

Possibly, but the meaning changes a bit.

• coger un libro can mean to take/pick up a book
• sacar un libro in a library context means to check out/borrow a book

So if you say:

• No puedo coger otro libro

it may sound more like I can’t take/pick up another book, not necessarily I can’t borrow another one officially.

In Spain, coger is a normal everyday verb, but for the library action, sacar is more precise here.

No puedo sacar otro libro means I can’t borrow another book right now. It describes a present inability.

• puedo = I can / I am able to

If you changed it to:

• No he podido sacar otro libro

that would mean I haven’t been able to borrow another book, which refers more to a recent past situation.

So the present tense fits the idea of a current problem: the speaker is at the library now, or speaking about the current situation.

Yes, exactly.

Se me olvidó el carné uses the preterite because the forgetting is seen as a completed event: at some point, the speaker forgot the card.

The sentence is presenting one finished fact that now causes a problem.

Compare:

• Se me olvidó el carné = I forgot the card
• Se me olvidaba el carné = I was forgetting the card / I used to forget the card

The imperfect would not fit as well here unless the context were very different.

Yes, but it means something slightly different.

• otro libro = another book, one more book
• más libros = more books

So:

• No puedo sacar otro libro = I can’t borrow another book
• No puedo sacar más libros = I can’t borrow any more books

The original sentence focuses on one additional book. The version with más libros is a bit broader.