Moja prijateljica živi u Rijeci.

Because moja has to agree with prijateljica.

In Croatian, words like moj / moja / moje change form to match the noun’s:

• gender
• number
• case

Prijateljica is a feminine singular noun, so the correct form is moja.

Compare:

• moj prijatelj = my male friend
• moja prijateljica = my female friend
• moje dijete = my child

So moja is the feminine singular form of my.

Prijateljica means female friend.

It is the feminine form of prijatelj, which means male friend or sometimes just friend in a general sense, depending on context.

• prijatelj = male friend
• prijateljica = female friend

For an English speaker, this is important because Croatian often marks the natural gender of people directly in the noun.

Because živi is a conjugated verb form, while živjeti is the infinitive.

• živjeti = to live
• živi = lives / is living

In this sentence, the subject is moja prijateljica, which is third person singular, so the verb must also be in the third person singular present tense:

• ja živim = I live
• ti živiš = you live
• on/ona živi = he/she lives

So Moja prijateljica živi... literally has the structure My friend lives...

Because Croatian often omits subject pronouns when they are not needed.

The verb form živi already tells you it is third person singular, and the noun moja prijateljica clearly tells you who the subject is.

So Croatian usually does not need a separate word like ona (she) here.

You could say:

• Moja prijateljica živi u Rijeci.
• Ona živi u Rijeci.

Both are correct, but the first one already identifies the subject, so adding ona would usually be unnecessary unless you want emphasis or contrast.

Because after u when it means in or at a location, Croatian uses the locative case.

The basic dictionary form is:

• Rijeka

But after u for location, it changes to:

• u Rijeci = in Rijeka

So:

• Rijeka = nominative
• u Rijeci = locative

This is one of the most important patterns in Croatian:

• u + locative for being somewhere
• u + accusative for going into somewhere

For example:

• Živim u Rijeci. = I live in Rijeka.
• Idem u Rijeku. = I’m going to Rijeka.

Rijeci is in the locative singular.

The sentence uses u to express location, and with location u normally takes the locative.

For the noun Rijeka, the singular forms include:

• Rijeka = nominative
• Rijeke = genitive
• Rijeci = dative/locative
• Rijeku = accusative
• Rijekom = instrumental

So in this sentence, Rijeci is specifically the locative form.

Not always. It often means in, but depending on context it can also correspond to English at or into.

Two very important uses are:

• u + locative = in/at a place
  
  • u Rijeci = in Rijeka
• u + accusative = into/to a place
  
  • u Rijeku = to/into Rijeka

So the meaning depends partly on the case that follows it.

Yes. Croatian word order is more flexible than English word order because the endings carry a lot of grammatical information.

The neutral, natural order here is:

• Moja prijateljica živi u Rijeci.

But other orders are possible for emphasis, for example:

• U Rijeci živi moja prijateljica.
  = In Rijeka lives my friend / My friend lives in Rijeka.
• Živi u Rijeci moja prijateljica.
  = more marked, used in certain contexts

Even though the word order can change, the basic meaning stays the same because:

• moja prijateljica is still the subject
• u Rijeci is still the location

A few Croatian letters in this sentence are especially useful:

• ž sounds like the s in measure
• j sounds like English y in yes
• lj is a single sound, somewhat like lli in million for many learners
• c is pronounced ts

So roughly:

• živi ≈ ZHEE-vee
• prijateljica ≈ pree-yah-TELY-ee-tsa
  (approximate only)
• Rijeci ≈ REE-yeh-tsee

These are only rough English approximations, but they can help you get started.

Yes, it is a normal declension pattern for many feminine nouns ending in -a.

A lot of feminine nouns in Croatian change the ending -a in the nominative to -i in the locative singular.

Examples:

• škola → u školi = in school
• soba → u sobi = in the room
• Rijeka → u Rijeci = in Rijeka

So once you learn that many feminine -a nouns behave this way, forms like u Rijeci start to feel much more predictable.

It specifically tells you the friend is female.

English my friend does not usually show gender. Croatian often does.

So if you say:

• moj prijatelj → the friend is male
• moja prijateljica → the friend is female

This is a common difference between Croatian and English.

No. Croatian does not have articles like English a/an and the.

So a sentence like:

• Moja prijateljica živi u Rijeci.

does not need any extra word corresponding to the.

Croatian usually expresses definiteness through context, word order, emphasis, or other wording—not with articles.

Yes, in informal speech you might hear frendica, which is a colloquial word meaning female friend.

• prijateljica = standard, neutral
• frendica = informal, conversational

So:

• Moja prijateljica živi u Rijeci. = standard Croatian
• Moja frendica živi u Rijeci. = more casual

For learners, it is best to know prijateljica first, since it is the standard form.