Sistem radi dobro.

Here radi means works, is working, or functions.

The verb is raditi, which often means:

• to work (as a person: I work)
• to function / operate (as a machine or system: The system works)

In Sistem radi dobro, it means the system is functioning properly.

Because sistem is third person singular: the system.

The present-tense forms of raditi are:

• ja radim — I work
• ti radiš — you work
• on/ona/ono radi — he/she/it works
• mi radimo — we work
• vi radite — you work / you all work
• oni/one/ona rade — they work

Since sistem is like it, Serbian uses radi.

Here dobro is an adverb, meaning well.

So:

• radi dobro = works well

This is similar to English:

• good = adjective
• well = adverb

In Serbian:

• dobar / dobra / dobro can be an adjective meaning good
• dobro can also be an adverb meaning well

In this sentence, it modifies the verb radi, so it is an adverb.

Serbian normally does not use articles like a or the.

So sistem can mean:

• a system
• the system

The exact meaning depends on context.

In this sentence, English might translate it as The system works well, but Serbian simply says Sistem radi dobro.

Because sistem is the subject of the sentence, so it is in the nominative case, which is the basic dictionary form.

This sentence has a very simple structure:

• Sistem — subject
• radi — verb
• dobro — adverb

Since sistem is doing the action, no other case is needed here.

Yes. This is the most neutral and natural word order:

• Sistem — subject
• radi — verb
• dobro — adverb

Serbian word order is fairly flexible, so you might also hear:

• Sistem dobro radi

That also means The system works well, but it puts a little more focus on dobro or sounds slightly more stylistic depending on context.

The standard beginner-friendly order is Sistem radi dobro.

A simple English-friendly approximation is:

SEE-stem RAH-dee DOH-broh

More roughly:

• Sistem = SEE-stem
• radi = RAH-dee
• dobro = DOH-broh

A few tips:

• Serbian r is usually rolled or tapped
• every vowel is pronounced clearly
• stress is not usually marked in normal spelling

Yes. Serbian present tense often covers both:

• works
• is working

So Sistem radi dobro can mean:

• The system works well
• The system is working well

Context tells you whether it is a general statement or something happening right now.

Yes, in some varieties of the language.

• sistem is very common and widely understood
• sustav is another word for system, especially common in Croatian

If you are learning Serbian specifically, sistem is the safest and most natural choice.

It is used for both.

Examples:

• Ja radim u školi. — I work at a school.
• Mašina radi. — The machine is working.
• Sistem radi dobro. — The system works well.

So raditi is a very useful verb because it can describe both human work and mechanical/technical functioning.

You add ne before the verb:

• Sistem ne radi dobro. — The system does not work well.

Very often, if something is completely broken, you may also hear:

• Sistem ne radi. — The system isn’t working.

Not in this sentence.

You need dobro because it describes how the system works, so you need an adverb.

• Sistem radi dobro. — correct = The system works well

If you used dobar, that would be an adjective, and it would need to describe a noun:

• Sistem je dobar. — The system is good

So compare:

• Sistem je dobar. = the system is good
• Sistem radi dobro. = the system works well