Struja ponovo radi.

In this sentence, struja means electricity or power supply.

Literally, the word can also mean current, as in electric current, but in everyday speech ima struje / nema struje / struja radi often refers to household electricity. So here it is best understood as the power.

Yes — radi is the 3rd person singular of raditi, which often means to work or to function.

In Serbian, it is very natural to say that electricity works/functions. So Struja ponovo radi literally means The electricity is working again, which is how Serbian commonly expresses The power is back on.

Radi is:

• present tense
• 3rd person singular
• from the verb raditi

It matches struja, which is singular.

So the structure is:

• struja = subject
• ponovo = adverb
• radi = verb

Because radi is already the main verb: works / is working.

English often uses to be + -ing, but Serbian usually does not need that kind of structure here. Present tense alone is enough.

So:

• Struja ponovo radi. = The power is working again / The power is back on.

You would not add je here.

Ponovo means again.

It is placed before the verb here, which is very natural in Serbian:

• Struja ponovo radi. = The power is working again.

The word order is fairly flexible, but this version sounds normal and neutral.

Yes. Opet also means again, and in everyday speech it is often even more common.

So you can say:

• Struja opet radi.
• Struja ponovo radi.

Both are correct.
Very roughly:

• opet = more conversational/common
• ponovo = slightly more neutral or formal

But in most situations, they are interchangeable.

Usually, yes.

In normal context, Struja ponovo radi strongly suggests that the electricity had stopped and has now come back.

So if the power was out and then returned, this is a natural sentence to say.

Serbian simply chooses a different natural expression.

English might say:

• The power is back on
• We have electricity again

Serbian often says:

• Struja radi. = The electricity is working.
• Struja je došla. = The power came back.
• Ima struje. = There is electricity.

So the Serbian sentence is normal even if it sounds a little more literal than the usual English phrasing.

Yes, absolutely. Došla je struja is a very common way to say The power came back.

These are both natural, but they emphasize slightly different things:

• Struja ponovo radi. = The electricity is working again
• Došla je struja. = The electricity/power has come back

If you are talking right after an outage, Došla je struja is extremely common.

Because Serbian has no articles like a or the.

So struja can mean:

• electricity
• the electricity
• sometimes even power

The exact meaning depends on context.

Yes, struja is a feminine noun.

That matters in some parts of Serbian grammar, especially with adjectives and past tense forms. In this sentence, though, it does not change the form of radi, because present-tense verb forms in Serbian do not change for gender.

So:

• struja = feminine noun
• radi = same present-tense form regardless of gender

A simple pronunciation guide would be:

STROO-ya po-NO-vo RA-dee

More closely:

• struja ≈ STROO-ya
• ponovo ≈ po-NO-vo
• radi ≈ RA-dee

A few helpful notes:

• j in Serbian sounds like English y
• r is rolled or tapped
• Serbian spelling is very phonetic, so words are usually pronounced much as they are written