Izljev vode je nevolja.

Because vode is the genitive singular form of voda.

In Croatian, many nouns that express:

• a quantity,
• a part of something,
• a flow/outpouring,
• or content,

are followed by the genitive.

So izljev vode literally means something like:

• an outflow of water
• a spill/discharge of water

This is similar to patterns like:

• čaša vode = a glass of water
• kap vode = a drop of water

So voda changes to vode because it depends on izljev.

Here is the case breakdown:

• izljev — nominative singular
• vode — genitive singular
• nevolja — nominative singular

Why?

• Izljev vode is the subject of the sentence, so izljev is in the nominative.
• Vode depends on izljev, so it goes into the genitive.
• After je with this kind of equational sentence, nevolja stays in the nominative too.

So the structure is basically:

[Subject in nominative] + je + [predicate noun in nominative]

Because in Croatian, when you use biti (to be) to say that one thing is another thing, the noun after je is usually in the nominative.

So:

• Izljev vode je nevolja. = A water leak/spill is a problem.

Both izljev and nevolja are nominative singular.

This is different from some languages where the second noun might take another case. In standard Croatian, with simple identification or classification like this, nominative is normal.

Croatian does not have articles like English a/an/the.

That means a sentence like Izljev vode je nevolja can mean different things depending on context, for example:

• A water leak is a problem
• The water leak is a problem
• Water leakage is a problem

The exact interpretation comes from the situation, not from an article.

This is very normal in Croatian, so learners have to get used to reading definiteness from context.

Je is the 3rd person singular present tense of biti (to be).

Since izljev is singular, the verb is singular too:

• izljev ... je ...

So the sentence structure is:

• Izljev vode = subject
• je = is
• nevolja = predicate noun

Very literally:

• Water outflow/leak is trouble/a problem.

Yes, Croatian word order is more flexible than English word order.

The neutral order here is:

• Izljev vode je nevolja.

But you could also say:

• Nevolja je izljev vode.

That changes the emphasis. It may sound like:

• The problem is a water leak or
• What the problem is, is a water leak

So both are possible, but they do not feel exactly the same in emphasis.

The original sentence is the most straightforward if you want to say that a water leak/spill is a problem.

Yes, it matters for agreement and for learning the noun patterns.

• izljev is masculine
• voda is feminine
• nevolja is feminine

In this particular sentence, gender does not change the form of je, because je is the same for all genders in the singular.

But gender matters for:

• adjectives,
• pronouns,
• and case endings.

For example:

• velik izljev = a big outflow/leak (masculine)
• hladna voda = cold water (feminine)
• velika nevolja = a big problem/trouble (feminine)

It can be understood, but it may sound a bit formal or technical depending on context.

Izljev more literally suggests:

• outflow
• discharge
• spill
• pouring out

If you mean a plumbing leak, Croatian often more naturally uses:

• curenje vode = water leaking / a water leak
• propuštanje vode = leaking of water

So:

• Izljev vode je nevolja is grammatically fine.
• But in everyday speech, if you mean a pipe or tap leak, Curenje vode je problem/nevolja may sound more natural.

Nevolja means something like:

• trouble
• a problem
• an inconvenience
• sometimes even misfortune, depending on context

In this sentence, it most naturally means:

• a problem or
• trouble

So nevolja is a bit broader than just a technical problem. It can sound slightly more emotional or human than problem.

Compare:

• To je problem. = That is a problem.
• To je nevolja. = That is trouble / That is a problem.

A rough pronunciation guide is:

• izljev ≈ EEZ-lyev

A few helpful points:

• i sounds like ee in see
• z is like z in zebra
• lj is a special Croatian sound, similar to the lli in some pronunciations of million, but cleaner and more distinct
• e is like e in met
• v is like English v

Also, Croatian spelling is very regular, so once you learn sounds like lj, pronunciation becomes much easier.

Yes. Because Croatian has no articles, the sentence can sound fairly general.

So depending on context, Izljev vode je nevolja might be interpreted as:

• A water leak is a problem
• Water leakage is a problem
• The water leak is a problem

If you want a clearly general statement, Croatian often prefers a more abstract noun such as curenje vode.

So a very natural generic statement would be:

• Curenje vode je problem.

But your original sentence can still be read generically if the context supports that.