U stanu nema struje.

Because u can take two different cases:

• Locative for location: u stanu = in the apartment
• Accusative for movement toward something: u stan = into the apartment

So in U stanu nema struje, we are talking about where something is or is not, not motion, so Serbian uses the locative.

Stanu is the locative singular of stan.

• stan = apartment / flat
• u stanu = in the apartment

This is a very common pattern:

• u gradu = in the city
• u školi = in the school
• u autu = in the car

Here nema means there is no or there isn’t any.

So the sentence is literally something like:

• U stanu nema struje.
• In the apartment, there is no electricity.

In natural English, that often becomes:

• There’s no electricity in the apartment.
• The apartment has no power.

This use of nema is extremely common for expressing absence.

Because after nema, Serbian normally uses the genitive.

• dictionary form: struja
• genitive singular: struje

So:

• ima struje = there is electricity / there is some power
• nema struje = there is no electricity / no power

This is one of the most important patterns to learn: absence often triggers the genitive.

Other examples:

• Nema vode. = There is no water.
• Nema mleka. = There is no milk.
• Nema vremena. = There is no time.

Yes.

• ima = there is / has
• nema = there is not / does not have

Compare:

• U stanu ima struje. = There is electricity in the apartment.
• U stanu nema struje. = There is no electricity in the apartment.

In sentences like this, ima/nema often work a lot like English there is / there isn’t.

Because Serbian does not need a dummy subject like English there.

English says:

• There is no electricity in the apartment.

Serbian simply says:

• U stanu nema struje.

So the idea of existence or absence is built into ima/nema, without adding a separate word for there.

Not always. Struja can mean:

• electric current
• electricity
• power supply
• sometimes even a current in water or air, depending on context

In this sentence, nema struje is a very common everyday phrase meaning:

• the power is out
• there’s no electricity

So this is exactly the kind of phrase you would hear during a power outage.

Yes. Serbian word order is more flexible than English.

The neutral version here is:

• U stanu nema struje.

But you could also hear:

• Nema struje u stanu.

Both mean basically the same thing. The difference is mainly one of focus or style.

• U stanu nema struje. → focuses first on the location
• Nema struje u stanu. → starts with the fact that there is no electricity

The original sentence sounds very natural.

Because Serbian has no articles.

English must choose between:

• an apartment
• the apartment
• electricity
• the electricity

Serbian simply says:

• stan
• struja

Context tells you whether it is definite or indefinite. In u stanu, English usually translates it as in the apartment or in the flat, depending on context.

Yes, but it is a slightly different structure.

• U stanu nema struje. = There is no electricity in the apartment.
• Stan nema struju. = The apartment doesn’t have electricity / power.

Both are understandable and natural, but the first is especially common when talking about a power outage.

Also note the case difference:

• nema struje → genitive after nema
• nema struju would not be correct in this meaning

With Stan nema struju, struju is the direct object of nema in a more personal, subject-based sentence.

Usually, yes.

In everyday speech, nema struje most often means:

• the power is out
• there’s no electricity right now

Depending on context, it could also mean the apartment simply has no electricity connection, but in normal conversation people usually understand it as a temporary lack of power.

The natural opposite is:

• U stanu ima struje. = There is electricity in the apartment.
• Ima struje. = There is power.

If you want to emphasize that the power has returned, you might also hear:

• Došla je struja. = The electricity came back. / The power came back.

That is a very common everyday expression in Serbian.