Ona sedi među prijateljima.

Because među here requires the instrumental case when it describes a location or a static situation.

So:

• prijatelji = friends
• među prijateljima = among friends

The ending -ima is the instrumental plural ending for this noun.

A learner often notices that Serbian changes noun endings a lot, and this is one of those cases: the preposition controls the case.

Because Serbian makes a distinction between:

• location / being somewhere → usually instrumental
• movement toward somewhere → often accusative

Here, the sentence describes a static situation: she is already sitting there. So:

• Ona sedi među prijateljima. = She is sitting among friends.

But with movement, you could get accusative, for example in a sentence meaning something like She sat down among her friends.

So the case helps show whether it is:

• where someone is or
• where someone goes

Sedi is the 3rd person singular present tense of the verb sedeti (to sit).

So:

• ja sedim = I sit / I am sitting
• ti sediš = you sit / you are sitting
• ona sedi = she sits / she is sitting

In Serbian, the present tense can often translate as either:

• sits
• is sitting

The exact English choice depends on context.

Yes. Serbian often drops subject pronouns when they are already clear from the verb form.

So both are possible:

• Ona sedi među prijateljima.
• Sedi među prijateljima.

The full pronoun ona is used when you want to:

• emphasize she
• make the subject especially clear
• contrast her with someone else

For example:

• On stoji, a ona sedi. = He is standing, and she is sitting.

So in many contexts, ona is optional.

No, Serbian word order is fairly flexible.

The neutral order here is:

• Ona sedi među prijateljima.

But depending on emphasis, you might also hear:

• Među prijateljima ona sedi.
• Sedi ona među prijateljima.
  (more marked, more contextual)

Even though the order can change, the case endings help show the relationships between words. That is one reason Serbian can be more flexible than English.

Not necessarily.

The plural prijatelji / prijateljima is grammatically masculine, but in Serbian that form can also be used for:

• a group of men
• a mixed group
• sometimes friends in a general sense

If you specifically mean a group of female friends, you would more explicitly say:

• prijateljicama = female friends

So među prijateljima often works as a general among friends, not only among male friends.

That is mainly a matter of regional/standard variation.

• sedi is the Ekavian form
• sjedi is the Ijekavian form

Both belong to standard Serbian, depending on the variety being used.

So:

• Ona sedi među prijateljima.
• Ona sjedi među prijateljima.

Both can be correct; they just reflect different pronunciation/standard usage.

A rough pronunciation guide:

• među ≈ MEH-joo, but with a special Serbian sound in the middle

The letter đ is pronounced somewhat like the j in juice, but softer. It is not exactly the same as any single English sound.

So među is not pronounced like:

• medju with a hard d
• or megu

It is a distinct Serbian consonant.

In this sentence, it is best translated as among.

Među can cover meanings like:

• among
• amid
• sometimes between, depending on context

With a plural noun like prijateljima, English usually prefers among:

• među prijateljima = among friends

If there were just two clearly separated people or things, English might prefer between, but Serbian can still use među more broadly than English sometimes does.

Because Serbian has no articles like English a/an/the.

So:

• prijateljima can mean friends, the friends, or even some friends, depending on context.

Serbian relies on:

• context
• word order
• stress/emphasis
• sometimes additional words

to express what English often shows with articles.

Yes.

The Serbian present tense often covers both:

• She sits among friends
• She is sitting among friends

Without more context, sedi can be understood either as:

• a general present or
• an action/state happening now

In real usage, context tells you which English version sounds most natural.

The dictionary form is prijatelj = friend.

From that, you get:

• singular nominative: prijatelj
• plural nominative: prijatelji
• plural instrumental: prijateljima

So when learning vocabulary, you would normally memorize the base form prijatelj, then learn how it changes by case and number.

Yes, but it means something slightly different in structure.

• Ona sedi među prijateljima. = She is sitting among friends.
• Ona je među prijateljima. = She is among friends.

The second sentence only tells you where she is, not what posture/action she has. The first sentence specifically says she is sitting.

So both are grammatical, but not identical.