Ona se smirila posle intervjua.

The dictionary form is smiriti se.

In this sentence, smirila is the feminine singular past form of that verb. When you look it up, include se, because smiriti and smiriti se do not mean exactly the same thing.

• smiriti = to calm someone/something
• smiriti se = to calm down

Se is a reflexive clitic. Here it is part of the verb smiriti se.

It often does not need to be translated as a separate English word like herself. In this sentence, smirila se most naturally means calmed down.

So:

• Ona je smirila dete. = She calmed the child.
• Ona se smirila. = She calmed down.

Usually it means she calmed down.

English often uses a simple intransitive verb here, while Serbian uses a reflexive form. Depending on context, it can sometimes feel close to she calmed herself down, but the normal translation is simply she calmed down.

This is a very common learner question.

With many verbs, Serbian forms the past tense with the auxiliary je:

• Ona je došla. = She came.

But with reflexive verbs in the 3rd person singular, Serbian normally says:

• Ona se smirila.

So je is not used here. You do not say Ona je se smirila.

Because it agrees with a feminine singular subject: ona.

In the Serbian past tense, this form shows gender and number:

• on se smirio = he calmed down
• ona se smirila = she calmed down
• ono se smirilo = it calmed down

So the -la ending tells you the subject is feminine singular.

It is genitive singular.

That is because the preposition posle normally takes the genitive case:

• posle časa = after class
• posle ručka = after lunch
• posle intervjua = after the interview

So the form is intervjua, not intervju.

Because intervju is a declinable noun in Serbian, even though it is a borrowed word.

Its nominative form is intervju, but after posle you need the genitive singular, which is intervjua.

So:

• intervju = nominative
• intervjua = genitive

This is normal for many loanwords in Serbian.

It could be omitted if the subject is already clear from context.

Serbian often leaves out subject pronouns:

• Smirila se posle intervjua.

That is very natural. Using ona can add clarity, contrast, or emphasis, for example if you are distinguishing her from someone else.

Because se is a clitic, and clitics usually go near the beginning of the clause, often in the second position.

So in:

• Ona se smirila posle intervjua.

Ona is the first element, and se comes right after it.

You cannot place se freely anywhere you want.

Smiriti se is perfective.

That means the sentence presents the action as a completed change of state: she became calm, the calming-down reached its result.

So smirila se means something like:

• she calmed down
• she settled down

If you wanted an ongoing or repeated idea, you would use an imperfective verb, such as smirivati se.

Serbian has no articles, so the phrase itself does not tell you the vs an.

Posle intervjua can mean either, depending on context. In many situations, English uses the interview because a specific interview is understood.

So Serbian leaves that distinction to context, not to an article.