Fanoušci zpívají refrén s kapelou.

The singular is fanoušek, meaning fan.

• fanoušek = one fan
• fanoušci = fans

So Fanoušci zpívají... means Fans are singing... or The fans sing...

Because it is the nominative plural form of fanoušek.

In this sentence, fanoušci is the subject, so Czech uses the nominative case.
The plural of fanoušek is irregular enough that you should simply learn it as:

• singular: fanoušek
• plural: fanoušci

This kind of change is very common in Czech noun declension.

Because it agrees with the plural subject fanoušci.

The infinitive is zpívat = to sing.
zpívají is the 3rd person plural present-tense form:

• já zpívám = I sing
• ty zpíváš = you sing
• on/ona zpívá = he/she sings
• my zpíváme = we sing
• vy zpíváte = you (plural/formal) sing
• oni/ony zpívají = they sing

Since fanoušci = they, the sentence needs zpívají.

It can mean both, depending on context.

Czech present tense often covers both:

• they sing
• they are singing

So Fanoušci zpívají refrén s kapelou can mean either:

• The fans sing the chorus with the band
• The fans are singing the chorus with the band

The exact English translation depends on the situation.

refrén is the direct object of the verb zpívají, so it is in the accusative case.

However, for many inanimate masculine nouns, the accusative singular looks exactly the same as the nominative singular.

So:

• nominative: refrén
• accusative: refrén

That is why the form does not visibly change here.

Because the preposition s meaning with requires the instrumental case.

The base form is:

• kapela = band

After s = with, it becomes:

• s kapelou = with the band

So this is a very important pattern to remember:

• s + instrumental

Examples:

• s kamarádem = with a friend
• s učitelkou = with a teacher
• s kapelou = with the band

The dictionary form is kapela.

Here is the relevant pair:

• kapela = band
• s kapelou = with the band

The ending -ou is a common instrumental singular ending for many feminine nouns ending in -a.

Yes. Czech word order is more flexible than English because cases show grammatical roles.

The neutral word order here is:

• Fanoušci zpívají refrén s kapelou.

But other orders are possible, for example to shift emphasis:

• S kapelou fanoušci zpívají refrén.
• Refrén zpívají fanoušci s kapelou.

These versions are still grammatical, but they may sound more marked or emphasize a different part of the sentence. For a learner, the original order is the safest and most neutral.

Because Czech has no articles.

English uses:

• the fans
• a band
• the chorus

Czech usually expresses these ideas without separate words like the or a. Context tells you whether something is definite or indefinite.

So:

• Fanoušci can mean fans or the fans
• refrén can mean a chorus/refrain or the chorus/refrain
• s kapelou can mean with a band or with the band

In this sentence, s means with.

That is the most important meaning for beginners, especially because it is followed by the instrumental case:

• s kapelou = with the band

Czech s can have other uses in other contexts, but here the meaning is clearly with.

You may also see se instead of s before some words, just for easier pronunciation:

• s bratrem
• se sestrou

But in your sentence, s kapelou is the normal form.

A simple learner-friendly pronunciation guide is:

Fanoušci zpívají refrén s kapelou
fa-NOHSH-tsi zpee-VAA-yee re-FRAYN s KA-peh-loh

A few useful pronunciation notes:

• š sounds like sh in shoe
• c sounds like ts
• zp at the start of zpívají is pronounced together
• é is a long vowel
• stress in Czech usually falls on the first syllable of each word

So roughly:

• FAnoušci
• ZPÍvají
• REfrén
• S kaPElou

In this sentence, refrén means the repeated part of a song, so it often corresponds to English chorus or refrain.

Both English translations can work, but:

• refrain is the more literal match
• chorus is often the more natural translation in everyday English

So zpívají refrén means they sing the refrain/chorus.

Usually it means singing with the band, and in natural English that can often be understood as singing along with the band.

So the sentence suggests that the fans are joining in while the band plays or sings. The exact nuance depends on context, but the basic idea is shared singing.

zpívat is imperfective.

That makes sense here, because the sentence describes an ongoing action or a general activity:

• Fanoušci zpívají... = The fans are singing / sing...

If you want the perfective partner, it is often zazpívat si or another context-dependent verb, but for the basic meaning to sing, learners should first remember:

• zpívat = imperfective = to sing / be singing

In this sentence, the imperfective verb is exactly what you would expect.