Kolegica je na bolovanju zbog leđa.

Kolegica means female colleague or female coworker.

It is the feminine form of kolega (male colleague, or sometimes colleague in a general sense depending on context). Croatian often marks gender directly in the noun, so if the speaker says kolegica, we know the person is female.

This also matches the rest of the sentence, since Croatian grammar often agrees with the gender of the person being talked about.

Je is the 3rd person singular present form of the verb biti (to be): is.

So:

• Kolegica je... = The female colleague is...

In Croatian, this short form je is a clitic, which means it usually appears in the second position in the sentence or clause. That is why it comes right after Kolegica.

Na bolovanju means on sick leave.

This is a fixed and very common Croatian expression. Literally, it is something like on sick leave / on medical leave.

You will often hear:

• biti na bolovanju = to be on sick leave
• otići na bolovanje = to go on sick leave
• vratiti se s bolovanja = to return from sick leave

So in this sentence, je na bolovanju is best understood as a whole idea: is on sick leave.

Croatian uses certain prepositions in fixed expressions, and na bolovanju is simply the standard idiomatic form.

Here, na does not literally mean physical location in the English sense. It is part of an established expression for being in a particular state or status, similar to:

• na odmoru = on vacation
• na porodiljnom = on maternity leave
• na fakultetu = at university / at the university (depending on context)

So this is something learners usually need to memorize as a chunk:

• biti na bolovanju

Bolovanju is in the locative singular.

That is because the preposition na can take different cases depending on meaning. Here it expresses a state or situation, not movement toward somewhere, so it takes the locative:

• na bolovanju = on sick leave

If there were movement toward something, na could take the accusative, but that is not what is happening here.

Zbog means because of, due to, or on account of.

It is followed by the genitive case. So in this sentence:

• zbog leđa = because of the back / because of back problems

This is a very common pattern:

• zbog posla = because of work
• zbog kiše = because of the rain
• zbog bolesti = because of illness

So one important thing to remember is:

• zbog + genitive

Yes, leđa is grammatically plural, but in Croatian it usually refers to the back as a body part.

This is a very important vocabulary point: leđa is a plural-only noun (often called pluralia tantum). Even though English says back in the singular, Croatian normally uses leđa.

So:

• bole me leđa = my back hurts
• imam problema s leđima = I have back problems
• zbog leđa = because of her/my/the back, depending on context

So although it looks plural, you should often translate it with singular back in English.

Yes, in context it usually means because of her back or because of back problems.

Croatian often does not use possessive words like her, his, or my when the meaning is obvious from context, especially with body parts and personal situations.

So Croatian may say:

• Bole me leđa. = My back hurts.
• Na bolovanju je zbog leđa. = She is on sick leave because of her back.

Adding a possessive is possible in some situations, but it is often unnecessary and less natural if the owner is already clear.

Most naturally, zbog leđa suggests because of back trouble / back problems / a back issue in a general sense.

It does not sound like it is talking about multiple backs. Because leđa is the normal Croatian word for back, the phrase is understood naturally.

If someone wanted to be more explicit, they might say:

• zbog problema s leđima = because of back problems
• zbog bolova u leđima = because of pain in the back
• zbog ozljede leđa = because of a back injury

But zbog leđa is concise and natural in everyday speech.

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

The neutral order here is:

• Kolegica je na bolovanju zbog leđa.

This sounds natural and straightforward.

You could also change the order for emphasis, for example:

• Zbog leđa je kolegica na bolovanju.
  Emphasis on the reason.
• Na bolovanju je kolegica zbog leđa.
  Less neutral, but possible in context.

However, the short verb form je is a clitic, so it still tends to stay near the beginning of the clause, in second position.

Yes, this sentence is natural.

A Croatian speaker could definitely say:

• Kolegica je na bolovanju zbog leđa.

It sounds like normal everyday language.

Depending on the situation, a speaker might also say:

• Kolegica je na bolovanju zbog problema s leđima.
  More explicit: The colleague is on sick leave because of back problems.
• Kolegica je na bolovanju zbog bolova u leđima.
  More specific: ...because of back pain.

But the original sentence is concise, idiomatic, and completely normal.

You would say:

• Kolega je na bolovanju zbog leđa.

The only change is:

• kolegica → kolega

Everything else stays the same, because:

• je still means is
• na bolovanju still means on sick leave
• zbog leđa still means because of back problems / because of his back

So the sentence structure remains the same; only the noun changes for gender.