Demà tornaré el llibre a la professora.

Demà means tomorrow, and Catalan often puts time expressions near the beginning of the sentence for clarity or emphasis.

So:

• Demà tornaré el llibre a la professora. = Tomorrow I will return the book to the teacher.

You could also hear other word orders, such as:

• Tornaré el llibre a la professora demà.

Both are possible, but starting with Demà is very natural.

Tornaré is the first person singular future form of tornar.

• tornar = to return / to give back / to come back, depending on context
• tornaré = I will return / I will give back

In this sentence, because there is a direct object (el llibre) and a recipient (a la professora), it clearly means I will return / give back the book.

Catalan usually forms the simple future by adding endings to the infinitive.

For tornar:

• tornaré = I will return
• tornaràs = you will return
• tornarà = he/she/it will return
• tornarem = we will return
• tornareu = you all will return
• tornaran = they will return

So tornaré = tornar + é.

The accent marks show stress and also help distinguish forms.

• Demà is stressed on the last syllable: de-MÀ
• tornaré is stressed on the last syllable: tor-na-RÉ

In Catalan, written accents are important because they often tell you where the stress falls and sometimes which vowel quality is intended.

Catalan often uses the definite article where English sometimes might omit it less naturally.

• el llibre = the book

In this sentence, it is a specific book that both speaker and listener can identify. So el llibre is the normal choice.

Articles in Catalan are used very regularly, so learners should get used to seeing them often.

A la professora means to the teacher.

It breaks down as:

• a = to
• la professora = the teacher

So:

• a la professora = to the teacher

This is the indirect object, the person receiving the book.

In this sentence, the teacher is the recipient of the book, so Catalan uses a to mark that idea of to.

Compare:

• el llibre = the thing being returned
• a la professora = the person it is being returned to

This is similar to English:

• I will return the book to the teacher

Yes. La professora is feminine and means the female teacher / the professor.

Compare:

• el professor = the male teacher/professor
• la professora = the female teacher/professor

Catalan nouns and articles show grammatical gender, so this sentence tells you the teacher is female.

Yes. Very often Catalan uses an indirect object pronoun.

You could say:

• Demà li tornaré el llibre.

Here:

• li = to him / to her / to you (formal singular)

So this means:

• Tomorrow I’ll return the book to her.

You can also combine both for emphasis or clarity:

• Demà li tornaré el llibre a la professora.

That is very natural in Catalan.

Because the verb ending already shows the subject.

• tornaré already means I will return

So jo is not necessary. Catalan often drops subject pronouns unless they are needed for emphasis, contrast, or clarity.

For example:

• Demà tornaré el llibre a la professora. = normal
• Demà jo tornaré el llibre a la professora. = emphasizes I

The word order can change, though some versions are more natural in certain contexts.

Common possibilities include:

• Demà tornaré el llibre a la professora.
• Tornaré el llibre a la professora demà.
• El llibre el tornaré demà a la professora.
  This version gives special emphasis to the book.

Catalan is flexible, but the original sentence is a very standard, neutral order.

No. Tornar has a few common uses.

It can mean:

1. to come back / return

   • Demà tornaré.
   • I’ll come back tomorrow.

2. to return / give back something

   • Demà tornaré el llibre.
   • I’ll return the book tomorrow.

3. In some expressions, it can also mean to do again

   • Torna-ho a dir.
   • Say it again.

So the exact meaning depends on the structure and context.

Llibre means book and is spelled with ll, a very common Catalan spelling.

A helpful approximate pronunciation is:

• LLI-breh

The ll sound varies somewhat depending on dialect and speaker. In many varieties, it sounds like a palatal ly-type sound, though in some modern speech it may sound closer to y.

The important thing for a learner is to recognize that ll is a normal Catalan letter combination and appears in many common words:

• llibre = book
• llengua = language
• fill = son

Yes, it sounds completely natural.

It is a straightforward sentence with:

• a time expression: Demà
• a future verb: tornaré
• a direct object: el llibre
• an indirect object: a la professora

A native speaker might also choose a pronoun version such as Demà li tornaré el llibre, but the full sentence you were given is clear, correct, and natural.