Opravdani trošak je visok.

• opravdani = justified, warranted, allowable, approved
• trošak = expense, cost
• je = is
• visok = high

So the whole sentence means something like The justified expense is high. In business or administrative contexts, opravdani trošak can also mean an allowable/eligible expense.

Because it agrees with trošak, which is masculine singular nominative.

In Croatian, adjectives must match the noun they describe in:

• gender
• number
• case

Here:

• trošak = masculine singular nominative
• opravdani = masculine singular nominative

Also, when an adjective comes before a noun like this, Croatian often uses the long form of the adjective, which is why you see opravdani rather than opravdan.

Because visok is being used as a predicate adjective after je.

A very useful beginner pattern is:

• before the noun: long form is common
  
  • visoki trošak = a high expense
• after the verb biti: short form is usual
  
  • trošak je visok = the expense is high

So in this sentence, visok is the natural form.

It is in the nominative singular because it is the subject of the sentence.

You can tell this from the structure:

• Opravdani trošak = the subject
• je visok = the predicate

The adjective opravdani matches trošak, so it is nominative singular too.

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 links the subject opravdani trošak with the description visok:

• The justified expense
  • is
    • high

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

That means the same Croatian phrase can often be translated in different ways depending on context:

• a justified expense
• the justified expense

Context tells you which one is meant.

Yes, very often it is.

In everyday language, opravdan means justified or reasonable. But in administrative, legal, tax, or accounting language, opravdani trošak often means something closer to:

• allowable expense
• eligible expense
• approved cost
• reimbursable expense depending on context

So it may sound slightly more technical than a simple everyday phrase.

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

The most neutral version is:

• Opravdani trošak je visok.

You may also hear other orders for emphasis, but they sound more marked:

• Trošak je visok. = The expense is high.
• Visok je opravdani trošak. = more literary or emphatic

So the original order is the safest and most natural one for a learner.

A simple pronunciation guide is:

• opravdani ≈ o-prav-da-nee
• trošak ≈ TRO-shak
• je ≈ ye
• visok ≈ vee-SOK

A few useful sound notes:

• š sounds like sh in ship
• j sounds like y in yes

So the whole sentence is roughly:

• o-prav-da-nee TRO-shak ye vee-SOK

Because Croatian, like English, uses high metaphorically for things like costs, prices, salaries, and rates.

So:

• visok trošak = high cost
• visoka cijena = high price
• visoka plaća = high salary

This is completely natural usage, just like English high cost.

This is an important vocabulary distinction.

• trošak = cost/expense from the point of view of the person who has to pay or bear it
• cijena = price as the amount something is sold for

So:

• Visok trošak = a high cost/expense
• Visoka cijena = a high price

In your sentence, trošak fits because the focus is on the expense itself, not the listed selling price.

Everything would have to agree with the plural noun.

Singular:

• Opravdani trošak je visok.

Plural:

• Opravdani troškovi su visoki.

Notice the changes:

• trošak → troškovi
• je → su
• visok → visoki

This shows how Croatian adjectives and the verb to be change to match number.