Pod pretpostavkom da je izvornik čitljiv, utvrdite istovjetnost.

Pod normally means under, but in expressions like pod pretpostavkom it means something like on the assumption or assuming.

Here, pretpostavkom is in the instrumental singular because the preposition pod can require the instrumental when it expresses a non-literal relation like this.

• pretpostavka = assumption
• pod pretpostavkom = under the assumption / assuming

So the phrase Pod pretpostavkom da... means Assuming that... or Provided that...

The combination da je introduces a clause meaning that ... is.

In this sentence:

• da = that
• je = is

So:

• Pod pretpostavkom da je izvornik čitljiv
  = On the assumption that the original is legible

This is very common in Croatian after nouns or expressions involving thinking, assuming, knowing, saying, etc.

Izvornik is a masculine noun meaning the original, usually in the sense of an original document, text, or source version.

In this sentence it is the subject of je čitljiv:

• izvornik = the original
• je čitljiv = is legible

So izvornik is the thing being described as legible.

Čitljiv agrees with izvornik.

Since izvornik is:

• masculine
• singular
• nominative

the adjective must also be:

• masculine
• singular
• nominative

So:

• izvornik = masculine singular noun
• čitljiv = masculine singular adjective meaning legible/readable

This is the standard predicative use after je:

• Izvornik je čitljiv.
• The original is legible.

Here utvrdite is best understood as the imperative of utvrditi.

It means:

• determine
• establish
• verify

In instructions, manuals, official procedures, and formal notices, Croatian often uses the 2nd person plural imperative to address:

• more than one person, or
• one person formally/politely

So utvrdite istovjetnost means something like:

• verify the identity
• establish sameness/correspondence

Although utvrdite can also look like a present-tense form, in this kind of sentence it functions as an instruction, so the imperative reading is the natural one.

Croatian uses the plural form not only for addressing several people, but also for formal singular address, similar to polite you.

So utvrdite can mean:

• you all, determine...
• or please determine... when speaking formally to one person

This is very common in official or instructional language.

The informal singular imperative would be:

• utvrdi

But that would sound too direct or too personal in a formal instruction.

Istovjetnost is a feminine noun meaning identity, sameness, or correspondence depending on context.

In practical or official language, utvrditi istovjetnost often means:

• to verify that two things are the same
• to establish identity
• to confirm a match

So the exact English wording depends on the situation. If the sentence is about documents, signatures, or copies, it may be closer to:

• verify identity
• confirm that they match
• establish authenticity/correspondence

The noun is in the accusative singular, but for this noun the accusative looks the same as the nominative:

• istovjetnost = nominative singular
• istovjetnost = accusative singular

Yes, it is quite a standard formal expression.

You will often see verbs like:

• utvrditi = establish, determine
• provjeriti = check
• potvrditi = confirm

with nouns like:

• istovjetnost = identity/sameness
• autentičnost = authenticity
• točnost = accuracy

So utvrditi istovjetnost sounds official and procedural, not casual. A learner should recognize it as bureaucratic or technical language.

The comma separates the introductory subordinate clause from the main clause.

Structure:

• Pod pretpostavkom da je izvornik čitljiv = subordinate clause
• utvrdite istovjetnost = main clause

Croatian normally uses a comma before or after subordinate clauses like this, especially when the dependent clause comes first.

So the comma here is completely standard.

Sometimes yes, but not always exactly.

• ako = if
• pod pretpostavkom da = under the assumption that / assuming that / provided that

Pod pretpostavkom da sounds more formal and a bit more explicit than plain ako. It suggests that the following instruction depends on that assumption being true.

So while English might sometimes simplify it to if, the Croatian phrasing is more formal and conditional in a bureaucratic way.

Because Croatian usually does not need an explicit subject pronoun.

The ending of the verb already tells you who is being addressed.

• utvrdite tells us this is you plural or formal you
• therefore Croatian does not need vi

If you added Vi, it would usually be for emphasis:

• Vi utvrdite istovjetnost.

But in a normal instruction, just utvrdite is enough.

The sentence has two parts:

1. Pod pretpostavkom da je izvornik čitljiv
   = an introductory condition/assumption
2. utvrdite istovjetnost
   = the main instruction

So the overall pattern is:

• Assuming that X is true, do Y.

This is a very useful pattern to recognize in formal Croatian.

Not really. It sounds formal, official, and somewhat bureaucratic.

Words and phrases that make it formal include:

• pod pretpostavkom
• izvornik
• utvrdite
• istovjetnost

In everyday speech, a Croatian speaker would probably use simpler wording unless they were dealing with documents, legal language, administration, or technical instructions.