Hún sór að koma aftur.

Hún is the 3rd person singular feminine pronoun, meaning she.

In this sentence, hún is the subject of the verb sór, so it appears in the nominative case.

• hún = she
• hana = her (object form)

So Hún sór... simply means She swore...

Sór is the past tense of the verb sverja, which means to swear.

This is an irregular verb, so the past tense does not look very similar to the infinitive:

• sverja = to swear
• sór = swore

This kind of vowel change is common in strong/irregular verbs in Icelandic.

Here, að is the infinitive marker, like English to in to come.

So:

• að koma = to come

In this sentence, sór að koma aftur means something like swore to come back.

Be aware that að can do several jobs in Icelandic, but here it is specifically marking the infinitive.

Because after the infinitive marker að, Icelandic normally uses the infinitive form of the verb.

So:

• að koma = to come
• kemur = comes / will come
• kom = came

Since the structure is sór að... (swore to...), the next verb stays in the infinitive: koma.

Icelandic often leaves out the subject in an infinitive phrase when it is understood to be the same as the subject of the main clause.

So Hún sór að koma aftur literally looks like:

• She swore to come back

But in English, depending on context, you might also translate it as:

• She swore that she would come back

The subject of koma is understood to be the same hún from the main clause.

Aftur usually means back or again.

In this sentence, with a verb of motion like koma, it most naturally means back:

• koma aftur = come back

In other contexts, aftur can also mean again:

• gera aftur can mean do again, depending on context

So the exact English translation depends on the verb and situation.

The basic order is very straightforward:

• Hún = subject
• sór = main verb
• að koma aftur = infinitive phrase

So the structure is:

• Subject + past tense verb + infinitive phrase

That is a very common Icelandic pattern.

Literally, sverja means to swear, so sór is swore.

So the most direct translation is:

• She swore to come back
• She swore that she would come back

However, in real usage it can sometimes overlap in meaning with a strong promise, depending on context. Still, learners should remember that the actual verb here is swear, not the ordinary verb promise.

Not directly in a word-for-word way.

In this sentence, að is grammatically the infinitive marker to, not the conjunction that. But when translating naturally into English, the whole phrase can sometimes come out as:

• She swore that she would come back

So the translation may use that, even though the Icelandic structure is still an infinitive construction.

A rough learner-friendly guide would be:

• Hún ≈ hoon
• sór ≈ sohr
• að ≈ ath or a softer uhth depending on speech
• koma ≈ KOH-ma
• aftur ≈ AF-tur

A very rough full approximation:

• hoon sohr ath KOH-ma AF-tur

A few notes:

• ú is a long oo-type sound
• ó is like o in go, but Icelandic pronunciation is not exactly the same as English
• ð is like voiced th in this, though in some positions it can be weaker

Yes. Very much so.

The pattern:

• [subject] + [past tense verb] + að + [infinitive]

is extremely common in Icelandic.

Examples of similar structures:

• Hún ætlaði að fara. = She intended to go.
• Ég reyndi að hjálpa. = I tried to help.
• Við vonumst til að vinna. = We hope to win.

So even if the specific verb sór is irregular, the overall construction is very useful and worth learning early.