Hún greiðir hárið sitt með nýjum hárbursta áður en hún fer út.

The ending -ið is the definite article attached to the noun.

• hár = hair
• hárið = the hair

In Icelandic, the definite article is usually added to the end of the noun instead of being a separate word like the in English.

Here, hárið is also in the accusative singular, because it is the direct object of greiðir.

sitt is a reflexive possessive pronoun, meaning her own in this sentence.

So:

• hárið = the hair
• hárið sitt = her own hair

Icelandic often uses this reflexive possessive when the possessor is the same as the subject of the sentence.

Since hún is the subject, sitt shows that it is her own hair that she is combing.

Use sinn / sín / sitt when the possessor is the same person as the subject.

So in this sentence:

• Hún greiðir hárið sitt = She combs her own hair

If you said hárið hennar, that would normally mean her hair belonging to some other female person, not necessarily the subject.

So the contrast is roughly:

• sitt = her own
• hennar = hers / her, but not reflexive

This is a very important distinction in Icelandic and often feels unusual to English speakers.

The form sitt matches the noun it refers to, not the subject.

The noun is hárið, which is:

• neuter
• singular
• accusative

So the reflexive possessive must also be neuter singular accusative, which is sitt.

The full set is:

• sinn for masculine
• sína for feminine
• sitt for neuter

So it is sitt because it agrees with hárið.

Because the preposition með normally takes the dative case when it means with.

So both the adjective and the noun must be in the dative:

• nýr hárbursti = a new hairbrush
• með nýjum hárbursta = with a new hairbrush

Here:

• nýjum = dative singular masculine of nýr
• hárbursta = dative singular of hárbursti

This is a very common pattern in Icelandic:

• preposition + required case

hárið is in the accusative because it is the direct object of the verb greiða.

The verb greiða in this meaning takes an accusative object:

• greiða hárið = to comb/brush the hair

So:

• hún = subject
• greiðir = verb
• hárið sitt = direct object in the accusative

Here greiðir is the present tense of greiða, and it means combs or brushes.

This verb can have several meanings in Icelandic depending on context, including:

• to comb / brush
• to pay
• to settle / arrange

But in greiða hárið, it clearly means to comb/brush one’s hair.

So learners need to rely on context with this verb.

Because Icelandic normally states the subject explicitly in the subordinate clause.

So:

• áður en = before
• hún fer út = she goes out

Even though English also repeats she here, English speakers sometimes wonder whether Icelandic could leave it out. In normal Icelandic, it is included.

út means out, and it works with fer to give the idea goes out.

• fer = goes
• fer út = goes out

Icelandic often uses adverbs or particles like this after motion verbs:

• fara inn = go in
• fara út = go out
• fara heim = go home

So út is an important part of the meaning here.

Because Icelandic commonly uses the present tense in clauses like this when talking about habitual or ordinary actions.

So:

• áður en hún fer út = before she goes out

This works very similarly to English. Even if the whole sentence describes a general routine, Icelandic still uses the present tense naturally here.

Yes, but it is quite normal Icelandic word order.

Main clause:

• Hún greiðir hárið sitt með nýjum hárbursta

This follows a standard pattern:

• subject + verb + object + prepositional phrase

Subordinate clause:

• áður en hún fer út

After a subordinating conjunction like áður en, Icelandic does not use the normal main-clause verb-second pattern. So hún comes before fer in the subordinate clause.

That is why:

• Hún greiðir ...
• áður en hún fer út

looks natural.

Yes. Here með means with, and the phrase tells you the instrument or means used to do the action.

So:

• greiðir hárið sitt með nýjum hárbursta = she combs/brushes her hair with a new hairbrush

This is a very common use of með in Icelandic.