Hún tekur af sér húfuna þegar hún kemur inn.

Literally, tekur af sér means takes off herself/from herself.

In natural English, we would simply say takes off. But Icelandic often expresses this idea with:

• taka = to take
• af = off, from
• sér = oneself / herself / himself / itself

So:

• Hún tekur af sér húfuna = She takes off her hat

It is a very common Icelandic pattern for removing clothes or things worn on the body.

Examples:

• taka af sér skóna = take off one’s shoes
• taka af sér jakkann = take off one’s jacket

Because sér is the reflexive pronoun. It refers back to the subject of the sentence.

Here, the subject is hún = she, so sér means herself.

• Hún tekur af sér húfuna = She takes off her own hat.
• If you used henni, that would normally mean her as a different female person, not the subject herself.

So Icelandic uses sér when the person doing the action and the person affected are the same person.

Compare:

• Hún tekur af sér húfuna.
  = She takes off her own hat.

• Hún tekur af henni húfuna.
  = She takes the hat off her (another woman/girl).

Sér is in the dative case.

That is because the preposition af normally takes the dative in Icelandic.

So in af sér:

• af = preposition
• sér = dative reflexive pronoun

This is worth remembering as a set phrase:

• af mér = off me / from me
• af þér = off you / from you
• af sér = off himself/herself/itself/from himself/herself/itself

Because húfuna is the definite accusative singular form of húfa.

Base form:

• húfa = a hat / cap

In this sentence, the hat is the direct object of tekur, so it appears in the accusative case. It is also definite, meaning the hat or her hat, so Icelandic adds the definite article to the end of the noun.

So:

• húfa = a hat
• húfuna = the hat

Why accusative?

• taka usually takes a direct object in the accusative.

So:

• Hún tekur húfuna = She takes the hat

And in the full sentence:

• Hún tekur af sér húfuna = She takes off her hat

Because Icelandic often does not need a possessive word where English uses one.

English says:

• She takes off her hat

Icelandic often prefers:

• Hún tekur af sér húfuna
• literally: She takes off herself the-hat

The idea of possession is already clear from sér, which shows that it is her own hat.

So Icelandic commonly uses:

• reflexive pronoun + definite noun

rather than:

• possessive adjective + noun

This is especially common with clothes, body parts, and personal belongings closely connected to the subject.

Yes, that is also possible.

Both patterns can occur:

• Hún tekur af sér húfuna
• Hún tekur húfuna af sér

The meaning is the same: She takes off her hat.

The difference is mostly about word order and emphasis. Icelandic allows some flexibility, especially with short prepositional phrases like af sér.

A learner should mainly recognize both. The version in your sentence is very natural and common.

Because the subordinate clause needs its own explicit subject.

The sentence has two clauses:

• Hún tekur af sér húfuna = She takes off her hat
• þegar hún kemur inn = when she comes in

Even though both clauses refer to the same person, Icelandic normally still says hún again.

So this is just normal grammar, not extra emphasis.

Þegar means when here. It introduces a time clause.

So:

• þegar hún kemur inn = when she comes in

It connects the two actions:

• she takes off her hat
• at the time that she comes in

In other contexts, þegar can also mean already, but not in this sentence.

Compare:

• Þegar hún kemur inn, tekur hún af sér húfuna. = When she comes in, she takes off her hat.
• Hún er þegar komin inn. = She is already inside.

Because koma inn is a verb + adverb combination meaning come in / come inside.

• koma = to come
• inn = in, inside

So:

• hún kemur inn = she comes in

This is very similar to English phrasal combinations like come in, go out, walk in, and so on.

You should learn koma inn as a common expression:

• Ég kem inn. = I come in / I’m coming in.
• Hann kom inn. = He came in.

Yes, kemur is present tense.

• koma = to come
• kemur = comes / is coming

Icelandic present tense often covers meanings that English expresses in different ways:

• simple present: comes
• present progressive: is coming

So þegar hún kemur inn can be understood as:

• when she comes in
• or, depending on context, when she is coming in

In a sentence like this, English usually prefers when she comes in.

Because þegar introduces a subordinate clause, and subordinate clauses in Icelandic normally keep ordinary subject-verb order.

So you get:

• þegar hún kemur inn not
• þegar kemur hún inn

This is different from main-clause word order, where Icelandic follows the verb-second rule.

For example, if the þegar-clause comes first, the main clause changes:

• Þegar hún kemur inn, tekur hún af sér húfuna.

Notice what happens in the main clause:

• tekur hún not
• hún tekur

That is because the first position is already occupied by the þegar-clause, so the verb comes next.

It can be either, depending on context.

Hún tekur af sér húfuna þegar hún kemur inn can mean:

• a habitual action: She takes off her hat when she comes in
• a narrative/present description: She takes off her hat when she comes in

Without more context, many learners will naturally read it as a habitual action.

Icelandic present tense often works well for repeated, usual actions.

No. Although af is related to English of historically, in modern Icelandic it often means things like:

• off
• from
• sometimes by or other meanings depending on context

In this sentence, af clearly means off:

• taka af sér húfuna = take off one’s hat

So it is better to learn prepositions by usage, not by trying to match each one to a single English word.

A useful breakdown is:

• Hún = she
  nominative subject

• tekur = takes
  present tense of taka

• af sér = off herself
  prepositional phrase; af

  • dative reflexive sér

• húfuna = the hat
  accusative singular definite of húfa

• þegar = when
  subordinating conjunction

• hún = she
  subject of the subordinate clause

• kemur inn = comes in
  present tense of koma

  • adverb inn

So the structure is basically:

She takes off her hat when she comes in.