Ovo je puknuće cijevi.

Word by word:

• Ovo = this
• je = is
• puknuće = rupture / burst / break
• cijevi = of the pipe or of a pipe

So the sentence is literally:

• This is a rupture of the pipe
• more naturally in English: This is a pipe rupture / This is a burst pipe situation

The exact English wording depends on context.

Because ovo is very commonly used as a standalone this in sentences like This is X.

In Croatian, when you identify something, you often use:

• ovo je = this is
• to je = that/it is
• ono je = that over there is

This is true even if the noun that follows is feminine or masculine.

For example:

• Ovo je moja sestra. = This is my sister.
• Ovo je cijev. = This is a pipe.

But if the demonstrative directly modifies the noun, then it must agree with the noun:

• ova cijev = this pipe
• ovaj zid = this wall
• ovo puknuće = this rupture

So:

• ovo je cijev = this is a pipe
• ova cijev = this pipe

Je is the 3rd person singular present tense of biti, which means to be.

So:

• ja sam = I am
• ti si = you are
• on/ona/ono je = he/she/it is

In this sentence, je simply means is:

• Ovo je... = This is...

Puknuće is a noun meaning a burst, rupture, break, cracking event.

It comes from the verb puknuti, which means to burst, to crack, to snap, or to break depending on context.

Examples:

• Cijev je pukla. = The pipe burst.
• puknuće cijevi = the rupture of a pipe / pipe rupture

Grammatically, puknuće is:

• neuter
• singular
• here in the nominative, because it is the predicate noun after je

It is a bit more noun-like and technical than the simple verb. English often uses a similar technical noun too: rupture.

Because cijevi is in the genitive singular.

The basic form is:

• cijev = pipe (nominative singular)

But after a noun like puknuće you often use the genitive to show of what:

• puknuće cijevi = rupture of a pipe / of the pipe

This is very common in Croatian. Compare:

• kraj filma = the end of the film
• početak sata = the beginning of the class/hour
• puknuće cijevi = the rupture of the pipe

So here:

• puknuće = rupture
• cijevi = of the pipe

Good question. Cijevi can indeed match more than one case form, depending on context.

For singular cijev, you can get:

• genitive singular: cijevi
• dative singular: cijevi
• locative singular: cijevi

But in puknuće cijevi, the meaning is clearly genitive because the structure is noun + genitive complement, meaning rupture of the pipe.

So although the form looks the same as dative/locative, the function here is genitive.

Croatian normally does not use articles like English a and the.

So cijev can mean:

• a pipe
• the pipe

and puknuće cijevi can mean:

• a pipe rupture
• the rupture of the pipe
• pipe rupture

Context tells you which meaning is intended.

That is why Croatian learners of English often struggle with articles, and English speakers learning Croatian often look for them even though they usually are not there.

Yes, it is understandable and correct, but it sounds a bit technical, formal, or like a label/description.

Ovo je puknuće cijevi sounds like:

• identifying a type of damage
• describing a problem in a report
• pointing to an image or diagram

In everyday speech, a Croatian speaker would very often say something simpler, such as:

• Pukla je cijev. = The pipe burst.
• Cijev je pukla. = The pipe burst.
• Došlo je do puknuća cijevi. = There was a pipe rupture. / A pipe burst occurred.

So the given sentence is correct, but not the most conversational choice in every situation.

Those are slightly different ideas in Croatian.

If you want to say The pipe burst, use a full clause with a verb:

• Cijev je pukla.
• or Pukla je cijev.

If you want to say This is a burst pipe, focusing on the damaged object, you would normally use an adjective-like form:

• Ovo je puknuta cijev.

So there is a useful difference:

• puknuće cijevi = the rupture/bursting of the pipe
  
  • focuses on the event or damage type
• puknuta cijev = a burst/broken pipe
  
  • focuses on the pipe itself

Yes, often there is.

Both are related to breaking/bursting, but they can feel slightly different:

• puknuće often refers to a single rupture, crack, or burst, often with emphasis on the result
• pucanje often refers more to the action/process of cracking/bursting, and in other contexts can also mean shooting

For a pipe problem, puknuće cijevi sounds more like a technical term: pipe rupture.

A rough pronunciation guide is:

• Ovo ≈ OH-vo
• je ≈ yeh
• puknuće ≈ POOK-noo-cheh, but with a softer ć sound than normal English ch
• cijevi ≈ TSYEH-vee

A few useful sound notes:

• j is like English y in yes
• c is like ts
• ć is a soft Croatian sound, somewhat like a very soft ch
• ije in cijevi is pronounced clearly, not like English spelling

So altogether, roughly:

OH-vo yeh POOK-noo-cheh TSYEH-vee

That is only an approximation, but it is a good start.