Eftir sturtu þvær hún hendurnar í handlauginni og fyllir baðkarið með heitu vatni fyrir dóttur sína.

Icelandic normally follows a verb-second pattern in main clauses. That means the finite verb usually comes in the second slot.

So when the sentence starts with Eftir sturtu (a time phrase), the verb þvær comes next, and the subject hún follows it:

Eftir sturtu | þvær | hún ...

If the sentence started with the subject, you would get:

Hún þvær hendurnar eftir sturtu ...

Both are possible, but when you move Eftir sturtu to the front, the verb has to stay in second position.

Eftir sturtu means after a shower / after showering in a general sense. It does not point to one specific shower.

If you said eftir sturtuna, that would mean after the shower, referring to a specific shower already known in the context.

Also, eftir requires an oblique case here, and sturtu is the correct singular form after that preposition.

So:

• eftir sturtu = after showering / after a shower
• eftir sturtuna = after the shower

Þvær is the present tense, 3rd person singular form of the verb þvo, meaning to wash.

So:

• ég þvæ = I wash
• þú þværð = you wash
• hún þvær = she washes

This is a verb with a vowel change, so the form does not look exactly like the infinitive þvo.

Hendurnar means the hands. Icelandic often uses the definite form with body parts where English would often use a possessive.

So Icelandic says:

þvær hendurnar = washes the hands

where English usually says:

washes her hands

In this sentence, the subject is already clear, so Icelandic does not need to add a separate word for her.

Using just hendur would sound less natural here.

Because Icelandic often expresses this idea differently from English.

With body parts, clothing, and similar things, Icelandic commonly uses the definite noun instead of a possessive pronoun when the owner is obvious from the context.

So:

• þvær hún hendurnar = she washes her hands
• literally closer to she washes the hands

The sentence already tells you that hún is the person doing the washing, so the ownership is understood.

These are examples of the Icelandic definite article attached to the end of the noun.

A few examples from the sentence:

• hendurnar = the hands
• handlauginni = in the sink / the sink in the required case
• baðkarið = the bathtub

The exact ending changes depending on:

• gender
• number
• case

So Icelandic does not usually have a separate word like English the. Instead, the is often built onto the noun itself.

Because í can mean either in with location or into with movement, and the case changes depending on that meaning.

Here the meaning is location:

in the sink

So Icelandic uses the form for location:

í handlauginni

Compare:

• í handlauginni = in the sink
• í handlaugina = into the sink

That location-versus-movement contrast is very important in Icelandic with prepositions like í.

Because með requires a particular case, and both the noun and the adjective have to match that case.

The base form is:

• heitt vatn = hot water

But after með, it changes to:

• með heitu vatni = with hot water

So both words change:

• heitt → heitu
• vatn → vatni

This is a very common Icelandic pattern: the adjective agrees with the noun in case, number, and gender.

Because sína is a reflexive possessive, and it refers back to the subject hún.

So:

fyrir dóttur sína = for her own daughter

If you said:

fyrir dóttur hennar

that would usually mean for her daughter, where her refers to some other female person, not the subject of the clause.

This is an important Icelandic distinction:

• sinn / sín / sitt = one’s own, referring back to the subject
• hans / hennar / þeirra = his / her / their, referring to someone else

The basic form of the word is dóttir = daughter, but here it comes after fyrir, so it changes form.

That is why you get:

• dóttir = daughter
• dóttur = daughter in the form required here

This is a very common feature of Icelandic: nouns change form depending on their grammatical role and the preposition used with them.

Because both verbs share the same subject.

So:

þvær hún hendurnar ... og fyllir baðkarið ...

means:

she washes her hands ... and fills the bathtub ...

Icelandic does not need to repeat hún here, just as English often does not repeat she in similar coordinated structures.

You could repeat it for emphasis, but it is not necessary.