Srce radi brzo.

Srce means heart.

In this sentence, it is in the nominative singular, which is the basic dictionary form used for the subject of the sentence. Here, srce is the thing doing the action, so it appears in nominative:

• Srce = heart
• Srce radi brzo = The heart works fast / The heart is functioning quickly

Also, srce is a neuter noun in Serbian.

Because many neuter nouns in Serbian end in -e or -o in the nominative singular.

So even though srce ends in -e, it is still singular.

Examples:

• more = sea
• dete = child
• srce = heart

This is completely normal for neuter nouns.

Radi is the present-tense form of the verb raditi.

The basic meaning of raditi is to work. In this sentence, radi means something like:

• works
• functions
• in context, possibly is working

So Srce radi brzo literally suggests The heart works fast or The heart is functioning quickly.

Depending on context, English might more naturally say The heart is beating fast, but that would more commonly be expressed in Serbian with a different verb.

Radi is:

• present tense
• 3rd person singular

That means it is used with subjects like:

• on = he
• ona = she
• ono = it
• singular nouns such as srce

So:

• Ja radim = I work
• Ti radiš = you work
• On/ona/ono radi = he/she/it works

Since srce is singular, radi is the correct form.

Because brzo is functioning as an adverb here, not an adjective.

It describes how the heart works:

• radi brzo = works quickly / works fast

Compare:

• brz = fast, quick (adjective, used with nouns)
• brzo = quickly, fast (adverb, used with verbs)

Examples:

• brz auto would try to mean fast car, though the correct phrase would be brz automobil
• Auto ide brzo = The car goes fast

So in Srce radi brzo, brzo modifies the verb radi.

Not usually.

A Serbian speaker would often say:

• Srce brzo kuca.

That is more natural if you mean The heart is beating fast.

Why?

• raditi = to work, function
• kucati = to beat, knock, tap

For a heart, kucati is often the more idiomatic verb when talking about heartbeat.

So:

• Srce radi brzo = The heart works/functions fast
• Srce brzo kuca = The heart beats fast

The sentence you were given is understandable, but learners should know that kuca is often the more natural choice in this specific context.

Because Serbian does not have articles like English a and the.

So srce can mean:

• a heart
• the heart
• just heart

The exact meaning depends on context.

In this sentence, English usually translates it as The heart works fast or The heart beats fast, but Serbian does not need a separate word for the.

No, Serbian word order is fairly flexible.

The neutral order here is:

• Srce radi brzo.

But you could also hear:

• Srce brzo radi.
• Brzo radi srce.

These versions can sound slightly different in emphasis:

• Srce radi brzo = neutral
• Srce brzo radi = slight emphasis on brzo
• Brzo radi srce = marked or poetic/emphatic, depending on context

So the given order is normal, but not the only possible one.

Yes, srce can be tricky for English speakers.

A rough pronunciation is:

• sr-tseh

The difficult part is the r. In Serbian, r can sometimes act almost like a syllable by itself, especially in words like srce.

Very roughly:

• s
• then a rolled or tapped r
• then ce, pronounced like tseh

So srce is approximately srt-seh, but with the r carrying the syllable more than in English.

Do not worry if it feels awkward at first. Words with syllabic r are common in Serbian and just take practice.

Yes.

Both of these are possible:

• Srce radi brzo.
• Srce brzo radi.

The difference is mostly about rhythm and emphasis, not basic meaning.

In everyday speech, adverbs like brzo are quite flexible in Serbian.

Not necessarily.

Without context, Srce radi brzo mainly suggests that the heart is working quickly or operating fast. That could describe:

• excitement
• fear
• exercise
• stress
• a medical issue

It does not automatically mean the heart is healthy or functioning well. It only tells you about speed, not whether that speed is good or bad.

The dictionary forms are:

• srce → srce = heart
• radi → raditi = to work
• brzo → usually connected with brz = fast, though brzo is the adverb form meaning quickly / fast

So if you were looking these up, you would search for:

• srce
• raditi
• brz

Yes, it is a complete sentence.

It has:

• a subject: srce
• a verb: radi
• an adverb: brzo

So grammatically it is fully complete.

Even though it is short, it is a normal Serbian sentence structure.