Mogu li posuditi ovu knjigu do petka?

Li is a question particle used to make a yes/no question in Croatian.

So:

• Mogu. = I can.
• Mogu li ... ? = Can I ... ? / May I ... ?

It does not translate as a separate English word. It simply helps turn the statement into a question.

In Croatian, li usually comes in the second position of the clause. This is a very common rule with short unstressed words called clitics.

So:

• Mogu li posuditi ovu knjigu do petka? is correct.
• Li mogu posuditi... is not correct.

A learner can often think of li as wanting to be near the beginning of the sentence, usually after the first stressed word.

Croatian often omits subject pronouns when they are already clear from the verb form.

• Mogu already means I can
• so ja is not necessary

You could say Ja mogu li..., but that is not natural here. The normal sentence is simply:

• Mogu li posuditi ovu knjigu do petka?

Croatian does this much more often than English.

Because ovu knjigu is in the accusative case, which is used for the direct object of the verb.

The basic form is:

• ova knjiga = this book (nominative)

But after a verb like posuditi when the book is the thing being borrowed, it becomes:

• ovu knjigu = this book (accusative)

Both the adjective/demonstrative and the noun change:

• ova → ovu
• knjiga → knjigu

This is very normal for feminine singular nouns in -a.

Because the preposition do requires the genitive case.

So:

• petak = Friday (basic form, nominative)
• do petka = until Friday / by Friday

This is a fixed pattern:

• do ponedjeljka = until Monday
• do sutra = until tomorrow
• do kraja = until the end

So the change from petak to petka is caused by the preposition do.

Usually it means until Friday, in the sense of up to Friday.

In context, with borrowing a book, English may also naturally say by Friday, meaning that the borrowing lasts up to that point and the book will be returned then or before then.

So the Croatian phrase do petka covers the idea of a deadline/end point.

Here, posuditi means to borrow.

So the sentence means asking permission to borrow the book.

A useful thing to know is that posuditi can sometimes mean either:

• to borrow
• or to lend

The meaning depends on the structure and context.

For example:

• Mogu li posuditi ovu knjigu? = Can I borrow this book?
• Možeš li mi posuditi ovu knjigu? = Can you lend me this book?

So the verb is the same, but the sentence pattern tells you whether the idea is borrowing or lending.

Posuditi is the perfective form. It refers to a single, complete action: borrowing the book.

That fits this sentence well, because the speaker is asking about one specific act of borrowing.

The imperfective form would be posuđivati, which is more about repeated, ongoing, or habitual action. That would not sound natural here in most situations.

So:

• posuditi = to borrow once / as a complete action
• posuđivati = to borrow repeatedly / habitually

For this sentence, posuditi is the normal choice.

Yes, it is a polite and natural way to ask.

Mogu li... ? is a common way to say:

• Can I ... ?
• May I ... ?

It is appropriate in everyday conversation and also polite enough in many normal situations, such as asking in a library, classroom, or from a friend.

If you wanted to sound especially formal or cautious, context and tone matter more than changing the grammar very much.

Yes, you could, but the nuance is a little different.

• Mogu li ... ? often asks about possibility/permission in a general way
• Smijem li ... ? more directly asks about permission

So:

• Mogu li posuditi ovu knjigu do petka? = Can I borrow this book until Friday?
• Smijem li posuditi ovu knjigu do petka? = Am I allowed to borrow this book until Friday? / May I borrow this book until Friday?

Both are possible, but Mogu li... is extremely common and natural.

Yes, Croatian word order is fairly flexible, though not completely free.

The neutral version is:

• Mogu li posuditi ovu knjigu do petka?

But you may also hear:

• Mogu li ovu knjigu posuditi do petka?

That version puts a little more focus on ovu knjigu.

What usually stays important is the position of li, which still comes after the first word or element:

• Mogu li ...
  not
• Mogu ... li in random later positions

So word order can shift for emphasis, but the standard sentence is already the most natural neutral form.

In standard Croatian, the normal construction here is with the infinitive:

• Mogu li posuditi ovu knjigu do petka?

The pattern with da + present tense is much more characteristic of some other South Slavic varieties, especially Serbian, and is less standard/natural in Croatian in this kind of sentence.

So if you are learning Croatian, it is best to use:

• mogu + infinitive

You would change ovu knjigu to a different demonstrative.

For example:

• ovu knjigu = this book
• tu knjigu = that book (near you / previously mentioned)
• onu knjigu = that book over there

So:

• Mogu li posuditi tu knjigu do petka?
• Mogu li posuditi onu knjigu do petka?

Notice that knjigu stays in the accusative; only the demonstrative changes.

A rough pronunciation guide for an English speaker is:

• Mogu ≈ MOH-goo
• li ≈ lee
• posuditi ≈ poh-soo-DEE-tee
• ovu ≈ OH-voo
• knjigu ≈ approximately KNYEE-goo
• do ≈ doh
• petka ≈ PET-kah

A few useful notes:

• g is always a hard g, as in go
• j sounds like English y
• lj and nj are special Croatian sounds; in knjigu, the nj is similar to the ny sound in some pronunciations of canyon

You do not need perfect pronunciation right away, but it helps to remember that Croatian spelling is much more regular than English spelling.