Puknuće cijevi nastaje zbog istrošenosti.

Puknuće is a verbal noun: a noun derived from the verb puknuti (to crack, burst, rupture).

In this sentence, puknuće names the event/result itself: a rupture / bursting / cracking.

A learner will often notice that Croatian can express an action either:

• with a verb: Cijev je puknula = the pipe burst
• or with a noun: Puknuće cijevi = the rupture of the pipe

So yes, it behaves like a noun here, but it comes from a verb.

Because cijevi is in the genitive singular.

The basic noun is:

• cijev = pipe

After a noun like puknuće, Croatian often uses the genitive to mean of ...:

• puknuće cijevi = rupture of the pipe

So:

• cijev = nominative singular
• cijevi = genitive singular

This is very common in Croatian noun phrases.

Yes, cijevi can also be nominative plural in other contexts.

For example:

• Cijevi su stare. = The pipes are old.

But in Puknuće cijevi, it is understood as genitive singular, because it depends on puknuće:

• rupture of the pipe

So the form is ambiguous by itself, but the sentence structure makes the meaning clear.

Nastaje means something like:

• arises
• occurs
• comes about
• develops

It is used here to describe how the situation comes into existence:

• Puknuće cijevi nastaje... = the rupture of the pipe occurs/arises...

This is a natural formal or technical way to describe cause and effect. It sounds more explanatory than simply using je (is).

Because the preposition zbog (because of / due to) requires the genitive case.

The base noun is:

• istrošenost = wear, worn condition, deterioration from use

After zbog, it becomes:

• istrošenosti = genitive singular

So:

• zbog istrošenosti = because of wear / due to wear

This is a very important pattern:

• zbog + genitive

Istrošenost is an abstract noun meaning:

• wear
• worn condition
• deterioration from use
• wear and tear (depending on context)

It comes from the adjective:

• istrošen = worn out, worn, used up

So:

• istrošen = worn
• istrošenost = wear / wornness / state of being worn

In technical or formal language, this kind of abstract noun is very common.

Yes, often there is a difference in nuance.

• puknuće usually refers more to the event/result: a crack, rupture, burst
• pucanje often refers more to the process/action of cracking or bursting

So:

• puknuće cijevi = the rupture/burst of the pipe
• pucanje cijevi = the pipe cracking/bursting, possibly focusing more on the process

In many contexts they may overlap, but puknuće sounds very natural in technical descriptions of a failure or break.

Sometimes od can also express cause, but here zbog is the more standard and neutral choice.

Compare:

• zbog istrošenosti = due to wear / because of wear
• od istrošenosti = can sometimes be understood, but is less standard here

In technical or explanatory writing, zbog is usually the safest choice.

Another formal alternative is:

• uslijed istrošenosti = as a result of wear

That sounds more formal or administrative.

Because Croatian has no articles like English a/an/the.

So cijev can mean:

• a pipe
• the pipe

The exact meaning is understood from context.

That means puknuće cijevi could be interpreted as:

• rupture of a pipe
• rupture of the pipe

Croatian leaves that unspecified unless context makes it clear.

No, Croatian word order is relatively flexible.

The given order:

• Puknuće cijevi nastaje zbog istrošenosti.

is neutral and natural.

But you could also reorder it for emphasis, for example:

• Zbog istrošenosti nastaje puknuće cijevi.

That puts more focus on the cause first.

The meaning stays basically the same, because the cases show how the words relate to each other.

You probably could be understood, but it sounds less natural.

Croatian prefers expressions like:

• Puknuće cijevi nastaje zbog istrošenosti.
• Do puknuća cijevi dolazi zbog istrošenosti.

These sound more idiomatic when explaining a cause.

Using je with zbog here feels more like a direct calque from English and less like natural technical Croatian.

A rough pronunciation guide is:

POOK-noo-cheh TSYEH-vee NAH-sta-yeh ZBOG ee-stroh-SHEH-no-stee

A few useful sound notes:

• ć in puknuće is a soft sound, somewhat like a softer ch
• c in cijevi is like ts
• j is like English y
• ž would sound like the s in measure, but this sentence has zbog, not žbog

You do not need perfect pronunciation to understand the grammar, but recognizing cije- as roughly tsye- helps a lot.