Learn Hardcore Croatian: On drži mobitel na stolu. - He keeps the phone on the table.

On drži mobitel na stolu. – grammatically correct, neutral, slight emphasis on he.
Drži mobitel na stolu. – also correct; context must make it clear that the subject is he.

You usually keep on/ona/oni when:

you want to contrast: On drži mobitel na stolu, a ona ga drži u torbi.
you introduce someone for the first time.

Otherwise it’s very natural to omit it.

What exactly does drži mean? Is it the same as has?

Drži is the 3rd person singular of držati, and it basically means to hold / to keep.

So:

On drži mobitel na stolu. – He keeps/holds the mobile phone on the table.

Nuance compared to English:

It’s closer to keeps than to simple has.
It suggests where he is keeping it (its position), not just possession.

If you want to say he owns a phone, you’d say:

On ima mobitel. – He has a mobile phone (he owns one).

Combining both ideas:

On ima mobitel i drži ga na stolu. – He has a mobile phone and he keeps it on the table.

Why is it drži and not another form of the verb?

Drži is the present tense, 3rd person singular form of držati.

Present tense of držati (informal standard):

ja držim – I hold/keep
ti držiš – you (sg) hold/keep
on/ona/ono drži – he/she/it holds/keeps
mi držimo – we hold/keep
vi držite – you (pl/formal) hold/keep
oni/one/ona drže – they hold/keep

Since the subject is on (he), you must use drži.

What is mobitel exactly? Is it the same as phone or smartphone?

In Croatian, mobitel means mobile phone / cell phone / smartphone. It covers what English speakers usually mean by phone when they’re talking about a mobile device.

You may also hear:

mobilni telefon – more formal or descriptive, literally mobile telephone
telefon – can mean any phone (landline or mobile), depending on context, but alone it more often suggests a landline if there’s no context.

In everyday Croatian, mobitel is the most common, natural word for a mobile phone.

Is mobitel in some special case here? Why is it just mobitel and not mobitela or something else?

Mobitel here is in the accusative singular, used for the direct object (the thing being held).

Mobitel is a masculine inanimate noun. Its nominative and accusative singular forms are the same:

Nominative (subject): Mobitel je na stolu. – The mobile is on the table.
Accusative (object): On drži mobitel. – He holds the mobile.

You get mobitela in other cases, for example:

Genitive: Nema mobitela. – There is no mobile (phone).

So in this sentence, mobitel is the correct accusative form.

Why is it na stolu and not na stol?

In Croatian, na can take two different cases, depending on meaning:

Location (where?) → na
- locative
- na stolu – on the table (it is already there, no movement)
Direction (onto where?) → na
- accusative
- na stol – onto the table (movement to the top of the table)

In On drži mobitel na stolu, you’re describing a static situation (where the phone is kept), so you use na stolu (locative), not na stol.

What case is stolu, and how does stol change in cases?

Stolu is locative singular of stol (table). With na meaning on in the sense of location, you use the locative.

Singular forms of stol (simplified):

Nominative: stol – table (subject)
Genitive: stola – of the table
Dative: stolu – to the table
Accusative: stol – (onto) the table (as object, with motion)
Locative: stolu – on/at the table (location, with na / u)
Instrumental: stolom – with/by the table

So na stolu literally means on (the) table in a stationary sense.

Can the word order change? For example, can I say Mobitel on drži na stolu or Mobitel drži na stolu?

Croatian word order is flexible, but On drži mobitel na stolu is the most neutral. Other options:

On mobitel drži na stolu. – puts slight emphasis on mobitel.
Mobitel drži na stolu. – drops on; focuses on mobitel as topic: The phone, he keeps it on the table.
Na stolu drži mobitel. – emphasizes the place: On the table, he keeps the phone.

Mobitel on drži na stolu is unusual in standard speech and sounds marked/weird unless you have a very specific contrastive context and intonation.

Generally, for learners, stick with:

On drži mobitel na stolu.
and then experiment with moving phrases to change emphasis once you’re comfortable.

Croatian only has one present tense. Does On drži mobitel na stolu mean He keeps the phone on the table (habit) or He is keeping the phone on the table (right now)?

The Croatian present covers both English present simple and present continuous.

On drži mobitel na stolu can mean:

He keeps the phone on the table (as a habit / generally).
He is keeping the phone on the table (right now).

Context or extra words show which is meant:

Uvijek drži mobitel na stolu. – He always keeps the phone on the table. (habit)
Sad drži mobitel na stolu. – Right now he is keeping the phone on the table. (current action)

Is there any way in Croatian to show the difference between a phone and the phone in this sentence?

Croatian has no articles (a, an, the), so mobitel can mean either a phone or the phone, depending on context.

On drži mobitel na stolu. could translate as:

He keeps *a mobile (phone) on the table.*
He keeps *the mobile (phone) on the table.*

You make it more specific by context or adding details:

On drži svoj mobitel na stolu. – He keeps *his mobile on the table.*
On drži taj mobitel na stolu. – He keeps *that mobile on the table.*

But there is no direct grammatical marking for a vs the.

Would the sentence change if we talked about a woman instead of a man?

Only the pronoun changes; the verb and the rest stay the same.

On drži mobitel na stolu. – He keeps the mobile on the table.
Ona drži mobitel na stolu. – She keeps the mobile on the table.

The verb drži does not change with gender; it only changes with person and number.