Već sam našla ključ.

Serbian commonly forms the past tense with:

• a present-tense form of biti (to be)
• plus a past participle

So:

• sam = I am (used here as an auxiliary)
• našla = past participle of naći (to find)

Together, sam našla means I found / I have found.

This is the normal way to express the past in Serbian:

• sam našla = I found / I have found
• si našla = you found
• je našla = she found

Because the participle agrees with the gender of the speaker.

• našla = said by a female
• našao = said by a male

So:

• Već sam našla ključ. = a woman is speaking
• Već sam našao ključ. = a man is speaking

This is very normal in Serbian past-tense forms.

Here, već means already.

So it shows that the action was completed before now, or earlier than expected.

Compare:

• Našla sam ključ. = I found the key.
• Već sam našla ključ. = I’ve already found the key.

In other contexts, već can sometimes have other meanings, but in this sentence it very clearly means already.

Because sam is a clitic in Serbian. Clitics usually go in the second position of the sentence or clause.

So in:

• Već sam našla ključ.

the first element is Već, and the clitic sam comes right after it.

This is a very common Serbian word-order pattern.

You can also say:

• Našla sam ključ.
• Ja sam već našla ključ.
• Ključ sam već našla.

These all shift emphasis a bit, but the placement of sam still follows clitic rules.

It comes from the verb naći (to find).

Its past participle changes form:

• našao = masculine singular
• našla = feminine singular
• našlo = neuter singular
• našli / našle = plural

So našla is the feminine singular past participle of naći.

Because ključ is the direct object here, so it is in the accusative case.

However, for masculine inanimate nouns, the accusative singular is usually the same as the nominative singular.

So:

• nominative: ključ
• accusative: ključ

That is why the form does not change.

Compare with a masculine animate noun:

• vidim čoveka = I see the man

But with an inanimate noun:

• našla sam ključ = I found the key

Because Serbian often drops the subject pronoun when it is already clear from the verb.

In sam našla, the person is already clear:

• sam tells you it is I
• našla also agrees with the speaker’s gender

So ja is not necessary.

You could add it:

• Ja sam već našla ključ.

But then it sounds more emphatic, like:

• I’ve already found the key.

It can correspond to either one, depending on context.

Serbian does not make the same strict distinction that English does between:

• I found
• I have found

The Serbian perfect often covers both ideas.

Because of već (already), English will often naturally use:

• I’ve already found the key.

But in some contexts, I already found the key could also work.

Because the sentence describes a completed action: the key has been found.

Serbian verbs come in aspects:

• naći = perfective (to find, completed result)
• nalaziti = imperfective (roughly to be finding, to find repeatedly, or used in ongoing/habitual contexts)

Since the result matters here, Serbian uses the perfective verb:

• Već sam našla ključ.

Using the imperfective would sound wrong or would change the meaning.

Yes, Serbian word order is fairly flexible, but the emphasis changes.

For example:

• Već sam našla ključ. = neutral, with focus on already
• Ključ sam već našla. = stronger focus on the key
• Našla sam već ključ. = possible, but less natural in many contexts
• Ja sam već našla ključ. = emphasis on I

Even though word order can move around, the clitic sam still has to follow the usual clitic-position rules.

Yes. Serbian has no articles like a and the.

So ključ can mean:

• a key
• the key

The exact meaning depends on context.

In this sentence, context often makes it sound like the key, especially if both speaker and listener already know which key is being talked about.