Podlaktica je na naslonu za ruke.

A natural word-by-word breakdown is:

• podlaktica = forearm
• je = is
• na = on
• naslonu = rest / support in a case form meaning on the rest
• za ruke = for arms

So the phrase naslon za ruke means armrest literally: a rest for arms.

A very literal translation would be:

Forearm is on the armrest.

In natural English, you would usually say:

The forearm is on the armrest
or
His/Her forearm is on the armrest, depending on context.

Podlaktica is the nominative singular form, which is the form used for the subject of the sentence.

Here, podlaktica is the thing being described, so it is the subject:

• Podlaktica = the forearm
• je na naslonu za ruke = is on the armrest

So Croatian uses the basic dictionary form here because the forearm is the subject.

Also, podlaktica is a feminine noun, which is why in other cases it will change like a typical feminine noun ending in -a.

Je is the 3rd person singular present tense of biti (to be).

So:

• ja sam = I am
• ti si = you are
• on/ona/ono je = he/she/it is

In this sentence, je means is.

Croatian often leaves out subject pronouns when they are not needed, so you do not need to say ona je unless you want emphasis. Just Podlaktica je... is completely normal.

Because na can take different cases depending on the meaning.

Here it expresses location: the forearm is on the armrest, not moving onto it.
When na shows a static location, Croatian normally uses the locative case.

So:

• naslon = nominative singular
• na naslonu = on the armrest (locative singular)

If there were movement onto something, Croatian would usually use the accusative instead.

Compare:

• Podlaktica je na naslonu. = The forearm is on the armrest.
• Stavio je ruku na naslon. = He put his hand onto the armrest.

Naslonu is the locative singular of naslon.

The noun naslon is a masculine noun, and after na meaning on in the sense of location, it goes into the locative:

• naslon = armrest / backrest / support
• na naslonu = on the armrest / on the support

This is one of the most important patterns to learn in Croatian:

• u + locative for being in
• na + locative for being on / at

Because za here means for, and in this kind of phrase it takes the accusative.

The base noun is:

• ruka = hand / arm

Its accusative plural form is:

• ruke

So:

• naslon za ruke = rest for arms = armrest

This is a fixed and very common type of Croatian structure:

• čaša za vodu = glass for water
• četka za kosu = brush for hair
• naslon za ruke = armrest

Even though English uses one word (armrest), Croatian often builds such meanings with noun + za + accusative.

Because Croatian and English do not always package meaning the same way.

English uses the compound noun armrest, which is singular in form.
Croatian expresses the idea more literally as a rest for arms, so the plural ruke is natural.

Also, ruka in Croatian can mean hand or arm depending on context. In naslon za ruke, the intended meaning is closer to arms.

So even though the English equivalent is singular-looking, Croatian uses:

• naslon za ruke = armrest

This is something you should learn as a vocabulary chunk.

Not always. Na often means on, but it can also mean at, to, or be used in other expressions.

For example:

• na stolu = on the table
• na poslu = at work
• na more = to the seaside
• na slici = in the picture / on the picture

What matters a lot is the case after it:

• na + locative = location, being on/at
• na + accusative = direction, movement onto/to

In your sentence, it is na + locative because the forearm is already resting there.

Yes. Croatian word order is more flexible than English word order.

The neutral order here is:

• Podlaktica je na naslonu za ruke.

But other orders are possible for emphasis, style, or context, for example:

• Na naslonu za ruke je podlaktica.
• Na naslonu za ruke podlaktica je. — possible, but less neutral

The most natural version for a basic statement is still:

• Podlaktica je na naslonu za ruke.

So as a learner, it is best to learn this neutral order first.

No. Croatian has no articles like English a and the.

So:

• podlaktica can mean a forearm or the forearm
• naslon can mean an armrest or the armrest

The exact meaning depends on context.

That is why Podlaktica je na naslonu za ruke can be understood as:

• A forearm is on an armrest
• The forearm is on the armrest

In real use, the surrounding context tells you which one is meant.

A simple approximate pronunciation for an English speaker is:

pohd-LAHK-tee-tsa yeh nah nah-SLOH-noo zah ROO-keh

A few useful pronunciation notes:

• c in Croatian is pronounced like ts
• j is pronounced like English y
• r is rolled or tapped
• vowels are usually clear and short, not reduced like in English

So:

• podlaktica ≈ pohd-LAHK-tee-tsa
• je ≈ yeh
• naslonu ≈ nah-SLOH-noo
• ruke ≈ ROO-keh

Yes, that is a very good idea.

Even though you can analyze it grammatically, learners benefit from memorizing naslon za ruke as a complete vocabulary item meaning armrest.

That helps you avoid trying to translate too literally from English every time.

So it is useful to know both:

• naslon = rest / support / backrest
• naslon za ruke = armrest

Learning common multi-word expressions as chunks is very helpful in Croatian.