Ova kratica mi je poznata, ali kad je stavim u navodnike, izgleda čudno.

Because kratica is a feminine noun, so the demonstrative must also be feminine.

• ovaj = this (masculine)
• ova = this (feminine)
• ovo = this (neuter)

So:

• ovaj stol = this table
• ova kratica = this abbreviation
• ovo slovo = this letter

Here, ova is nominative feminine singular, matching kratica.

Kratica means abbreviation.

It is a feminine noun. In this sentence, it refers to a shortened written form, like an acronym or abbreviation. Depending on context, English might translate it as abbreviation, acronym, or short form, but abbreviation is the safest general meaning.

Here mi is the unstressed dative form of ja and means to me.

So Ova kratica mi je poznata literally means:

This abbreviation is familiar to me.

That is a very natural Croatian way to express the idea I know this abbreviation or This abbreviation is familiar to me.

A useful pattern is:

• To mi je poznato. = That is familiar to me.
• Ona mi je poznata. = She/it is familiar to me.

So Croatian often uses poznat + dative person instead of using a verb like English know.

Because poznata is an adjective agreeing with kratica.

Since kratica is:

• feminine
• singular
• nominative

the adjective must match it:

• poznat = masculine
• poznata = feminine
• poznato = neuter

So:

• Ovaj izraz mi je poznat.
• Ova kratica mi je poznata.
• Ovo ime mi je poznato.

No. They just happen to look the same.

1. In mi je poznata, je means is.
   It is the 3rd person singular present of biti = to be.

2. In kad je stavim u navodnike, je means it.
   It is the unstressed accusative pronoun referring back to kratica.

So the sentence contains:

• je = is
• je = it

That is a very common source of confusion for learners.

You could expand the second part to see it more clearly:

• kad kraticu stavim u navodnike = when I put the abbreviation in quotation marks

The pronoun je is standing in for kraticu.

Both are correct.

• kad = shorter, very common in everyday speech and writing
• kada = fuller form, sometimes a bit more formal or emphatic

So:

• kad je stavim...
• kada je stavim...

Both work here. In ordinary modern Croatian, kad is very natural.

Because stavim is from the perfective verb staviti, while stavljam is from the imperfective stavljati.

Here Croatian prefers the perfective form because the idea is when I put it in quotation marks as a complete action.

• staviti = to put, to place (completed action)
• stavljati = to be putting, to put repeatedly/habitually/processually

After kad, Croatian often uses the present tense of a perfective verb for actions that are understood as future or whenever-type completed events.

So kad je stavim u navodnike is very natural.

If you said kad je stavljam u navodnike, it would sound more like focusing on the ongoing process, which is not the point here.

Because Croatian uses:

• u + accusative for movement into something
• u + locative for being in something

Here the idea is metaphorically putting the abbreviation into quotation marks, so Croatian uses the accusative:

• stavim je u navodnike = I put it in quotation marks

Compare:

• Riječ je u navodnicima. = The word is in quotation marks.
  Here it is already there, so u navodnicima is locative.

This is the same general pattern as:

• Idem u školu. = I am going to school.
• U školi sam. = I am at school.

Because navodnici means quotation marks, and that is normally treated as a plural noun in Croatian.

So the standard expression is:

• staviti u navodnike = to put in quotation marks

The form navodnike is accusative plural, because it follows u with the idea of movement into something.

Because čudno is the natural choice when talking about how something looks/seems overall.

With verbs like:

• izgledati = to look/seem
• zvučati = to sound
• djelovati = to seem/come across

Croatian very often uses the neuter/adverb-like form:

• izgleda čudno = it looks odd
• zvuči dobro = it sounds good
• djeluje ozbiljno = it seems serious

Here izgleda čudno means the written result looks odd or strange.

If you said izgleda čudna, that would sound more like you are describing the abbreviation itself as a strange feminine thing. That is not impossible in every context, but izgleda čudno is much more natural here.

Because Croatian unstressed pronouns and auxiliary forms usually follow strict clitic placement rules.

In kad je stavim:

• je = unstressed object pronoun
• stavim = main verb

These short unstressed words, called clitics, tend to appear near the beginning of their clause, usually in second position.

That is why Croatian says:

• kad je stavim u navodnike

rather than placing the pronoun later in the clause.

Croatian word order is flexible, but clitics are one of the areas where the language has fairly strong rules.

There are two reasons:

1. A comma before ali
   Croatian normally puts a comma before coordinating conjunctions like ali when joining clauses.

2. A comma after kad je stavim u navodnike
   That whole part is a subordinate time clause: when I put it in quotation marks. It is followed by the main clause izgleda čudno, so a comma is used.

So the structure is:

• Ova kratica mi je poznata,
• ali kad je stavim u navodnike,
• izgleda čudno.

Yes, but it is a little different in style and nuance.

• Ova kratica mi je poznata = This abbreviation is familiar to me.
• Znam ovu kraticu = I know this abbreviation.

Both are understandable, but the original sentence sounds very natural and idiomatic in Croatian. It focuses on familiarity rather than direct knowledge.

Croatian often prefers expressions with poznat in situations where English might simply use know.