Njen glas je dobar.

Njen means her and is a possessive adjective in Serbian. It agrees with the noun it describes in gender, number, and case.

Here it describes glas (voice), which is:

• masculine
• singular
• nominative

So the correct form is njen glas = her voice.

Because Serbian possessive words change form to match the noun.

Since glas is a masculine singular noun, the possessive must also be in the masculine singular nominative form:

• njen glas = her voice

Compare:

• njena kuća = her house (kuća is feminine)
• njeno dete = her child (dete is neuter)

So njena glas is wrong because glas is not feminine.

In Serbian, every noun has a grammatical gender: masculine, feminine, or neuter.

Glas is a masculine noun. One clue is that many masculine nouns in the dictionary form end in a consonant, and glas does.

Because it is masculine, adjectives and possessives referring to it must also be masculine:

• njen glas
• dobar glas

Because adjectives also agree with the noun they describe.

Since glas is:

• masculine
• singular
• nominative

the adjective must also be:

• masculine singular nominative

So:

• dobar glas = a good voice

Other forms would be used with different genders:

• dobra knjiga = a good book
• dobro vino = good wine

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

So:

• Njen glas je dobar. literally has the structure:
• Her voice is good.

In Serbian, unlike in Russian for example, the verb to be is normally expressed in the present tense in this kind of sentence.

Yes. Serbian word order is more flexible than English word order, although not completely free.

The neutral, standard order is:

• Njen glas je dobar.

You may also hear:

• Dobar je njen glas.
• Njen je glas dobar.

These alternatives can shift emphasis or sound more literary or contrastive. For a learner, Njen glas je dobar is the safest and most natural basic pattern.

Serbian has no articles like the or a/an.

So nouns do not automatically show definiteness the way English does. Context tells you whether something is definite or indefinite.

Here, because of njen (her), the noun is naturally understood as definite:

• njen glas = her voice

Possessives usually make the noun specific.

Yes. Njen and njezin both mean her.

In many varieties of Serbian, njen is more common, but njezin is also understood and used, especially depending on region, style, or neighboring standard varieties.

So both can mean:

• Njen glas je dobar.
• Njezin glas je dobar.

For a beginner learning standard Serbian, njen is a very normal choice.

Dobar usually means good, but exactly what that means depends on context.

With glas, it could suggest:

• pleasant
• strong
• nice-sounding
• of good quality for speaking or singing

So the exact nuance comes from the situation. Grammatically, though, it is simply the adjective good.

A practical approximation is:

• njen ≈ nyen

The nj sound is a single Serbian consonant, similar to the ny sound in canyon for many English speakers.

So:

• njen sounds roughly like nyen
• glas sounds roughly like glahs
• dobar sounds roughly like DOH-bar

Also, Serbian spelling is very regular, so pronunciation usually matches writing closely.

The sentence is in the nominative for the noun phrase and predicate adjective.

• njen — nominative singular masculine
• glas — nominative singular
• dobar — nominative singular masculine

This is because glas is the subject of the sentence, and predicate adjectives after je commonly appear in the nominative in this type of sentence.

Yes. Glas je dobar is a perfectly grammatical sentence and means The voice is good or A voice is good, depending on context.

Adding njen makes it specific:

• Glas je dobar. = The voice is good / A voice is good
• Njen glas je dobar. = Her voice is good

So njen is not required for grammar, but it changes the meaning.