Celý svět zná tuto píseň.

Celý svět means the whole world or the entire world.

• svět = world
• celý = whole, entire

So Celý svět zná tuto píseň is stronger than just Svět zná tuto píseň. It gives the sense that everyone everywhere knows it.

Also, celý has to agree with svět:

• svět is masculine inanimate singular
• so the adjective takes the form celý

Czech does not use articles like a / an / the.

So:

• svět can mean world or the world
• tuto píseň can mean this song

Czech relies on:

• context
• word order
• demonstratives like ten, ta, to (this/that depending on usage)

That is why Celý svět zná tuto píseň naturally translates as The whole world knows this song, even though there is no separate word for the.

Tuto píseň is in the accusative case, because it is the direct object of the verb zná (knows).

The verb znát takes a direct object in the accusative:

• znát koho/co = to know whom/what

Here:

• kdo? co? knows = celý svět → the subject
• knows what? = tuto píseň → the direct object, so accusative

So:

• tato píseň = this song (nominative)
• tuto píseň = this song (accusative)

Because tuto is the accusative feminine singular form of tato.

The noun píseň is:

• feminine
• singular

And in this sentence it is the object, so it must be in the accusative.

Forms of this for feminine singular:

• tato = nominative
• tuto = accusative

So:

• Tato píseň je krásná. = This song is beautiful.
• Znám tuto píseň. = I know this song.

You may also sometimes hear tu píseň instead of tuto píseň. Both are possible, but tuto can sound a bit more explicit or formal.

Good question. In this noun pattern, píseň has the same form in the nominative and accusative singular.

So:

• nominative: píseň
• accusative: píseň

What shows the case clearly here is mostly the demonstrative:

• tato píseň = nominative
• tuto píseň = accusative

This is normal for many Czech nouns: sometimes the ending changes between cases, and sometimes it does not.

Zná is the 3rd person singular form of znát, meaning knows or is familiar with.

So:

• já znám = I know
• ty znáš = you know
• on/ona/ono zná = he/she/it knows

In this sentence, the subject is celý svět, which is grammatically singular, so the verb is singular too:

• Celý svět zná...

Even though the whole world refers to many people, the noun svět itself is singular, so Czech uses zná, not a plural form.

Because Czech grammar follows the grammatical subject, not the idea of how many people are included.

The subject here is:

• svět = world
• grammatically singular

So the verb must also be singular:

• Celý svět zná...

This is similar to English:

• The whole world knows this song.

English also uses knows, not know, because world is singular.

This is one of the most important distinctions in Czech.

Use znát for being familiar with:

• a person
• a place
• a song
• a book
• a film
• something you recognize or know from experience

Use vědět for knowing a fact or piece of information.

So:

• Znám tuto píseň. = I know this song / I’m familiar with this song.
• Vím, že ta píseň je stará. = I know that the song is old.

You would not normally use vědět in Celý svět zná tuto píseň, because the meaning is not the whole world knows a fact, but the whole world is familiar with this song.

Yes. Czech word order is more flexible than English, because case endings show grammatical roles.

The neutral order here is:

• Celý svět zná tuto píseň.

But you could also say:

• Tuto píseň zná celý svět.

That version puts more emphasis on this song:

• This song, the whole world knows.

So the meaning stays basically the same, but the focus changes.

It can sound a little more careful or formal than some everyday alternatives.

Common possibilities include:

• tuto píseň
• tu píseň
• in informal spoken Czech, sometimes people might prefer a colloquial structure like tuhle píseň

Very roughly:

• tuto píseň = standard, clear, slightly more formal/emphatic
• tu píseň = standard and common
• tuhle píseň = more colloquial spoken Czech

So the sentence is perfectly normal Czech, but in casual speech some speakers might choose a different demonstrative form.

A few pronunciation points are useful here:

• Celý: ce- sounds like tse
• svět: the ě changes the sound of the preceding consonant, so svět is roughly like svyet with a softened s/v cluster
• zná: long á
• tuto: stress is on the first syllable, as usual in Czech
• píseň: long í, and eň has a softened n

Important pronunciation rules:

• Czech stress is usually on the first syllable
• á and í are long vowels
• ň is a soft n sound

A rough English-style approximation might be:

• TSE-lee svyet znaa TOO-to PEE-sen But that is only approximate.

Yes, it matters because adjectives must agree with nouns.

svět is:

• masculine inanimate
• singular

That is why the adjective is:

• celý and not some other form

For example, compare:

• celý svět = the whole world
• celá kniha = the whole book
• celé město = the whole city

The ending of celý changes depending on the gender and case of the noun.

Yes, that is a very natural English equivalent.

Literally, the sentence means:

• The whole world knows this song

But idiomatically, it often implies:

• Everyone knows this song
• This song is known everywhere
• This song is famous worldwide

So depending on context, English may translate it more naturally in different ways, even though the Czech wording stays the same.