Gde je moj telefon?

Because telefon is a masculine singular noun in Serbian.

Possessive words like moj must agree with the noun they describe:

• moj = masculine singular
• moja = feminine singular
• moje = neuter singular

So:

• moj telefon = my phone
• moja knjiga = my book
• moje dete = my child

Since telefon is masculine, moj is the correct form.

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

So here it means is.

A very literal structure is:

• Gde = where
• je = is
• moj telefon = my phone

So the sentence is built the same basic way as English Where is my phone?

This is because je is a clitic in Serbian. Clitics are short, unstressed words that usually like to stand in the second position in a clause.

So in a normal question:

• Gde je moj telefon?

Here, Gde is first, and je comes right after it.

For an English speaker, this can feel unusual at first, but it is very normal in Serbian.
A version like Gde moj telefon je? sounds unnatural in standard Serbian.

Yes. Telefon is in the nominative case, because it is the subject of the sentence.

The question is basically asking where the phone is, so telefon is the thing being talked about as the subject.

In this sentence, the nominative form is simply:

• telefon

There is no extra ending here, so the basic dictionary form is used.

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

So Serbian often uses the noun by itself, and the exact meaning comes from context.

For example:

• telefon can mean a phone or the phone
• moj telefon clearly means my phone

English speakers often expect an article, but in Serbian you normally do not need one.

Yes, you can.

• Gde je telefon? = Where is the phone?
• Gde je moj telefon? = Where is my phone?

If you leave out moj, the sentence becomes less personal and depends more on context.
With moj, you clearly show possession.

So if you are specifically looking for your own phone, moj is perfectly natural.

Yes, and it is very common in everyday Serbian.

• Gde je moj telefon?
• Gde mi je telefon?

Both can mean Where is my phone?

The second version uses mi, which is the dative form of ja (I/me).
Literally, it is something like Where is the phone to me?, but in natural English that becomes Where is my phone?

This dative-possessor structure is extremely common in Serbian, especially in speech. In many everyday situations, Gde mi je telefon? may sound a bit more natural and conversational.

Here is a simple breakdown:

• Gde = question word (where)
• je = verb (is)
• moj = possessive adjective (my)
• telefon = noun (phone)

So the structure is:

• question word + verb + possessive + noun

Even if the meaning is already clear to you, this breakdown helps you see how Serbian builds the sentence.

A rough English-friendly guide is:

gde yeh moy telefon

A few helpful points:

• gde: the g and d are both pronounced; Serbian spelling is very phonetic
• j in Serbian sounds like English y
• je sounds roughly like ye
• moj sounds roughly like moy
• telefon is pronounced clearly syllable by syllable: te-le-fon

A good habit is to read Serbian exactly as written, because spelling and pronunciation match much more closely than in English.

You may see other forms, depending on region and standard variety.

• gde is the common Serbian form, especially in Ekavian
• gdje appears in Ijekavian varieties
• kde exists in some dialects, but it is not the usual standard Serbian form here

So for standard Serbian, Gde je moj telefon? is completely correct and natural.

Yes, absolutely.

Gde je moj telefon? is a normal, clear sentence and sounds natural.

In casual speech, though, many speakers might more often say:

• Gde mi je telefon?

Both are correct.
The version with moj is especially useful for learners because it shows possession very clearly.