Hún setur vatnsflöskuna á klettinn og leitar svo að öðrum gönguskónum sínum.

In Icelandic, the is usually not a separate word. It is attached to the end of the noun as a suffix.

So here:

• vatnsflöskuna = the water bottle (accusative form)
• klettinn = the rock (accusative form)
• gönguskónum can mean the hiking shoe or the hiking shoes in this form

That is one of the biggest differences from English.

Because Icelandic loves compound nouns.

vatnsflaska = vatn (water) + flaska (bottle)

The -s- is a linking element here, historically related to the genitive of vatn. So the whole compound literally works like water-bottle.

Then the ending changes because of grammar:

• vatnsflaska = a water bottle
• vatnsflöskuna = the water bottle (accusative singular)

Setja is the infinitive, meaning to put / to set.

In the sentence, the verb is conjugated for she:

• ég set = I put
• þú setur = you put
• hún setur = she puts

So hún setur means she puts.

Because á can take different cases depending on meaning.

• accusative after á usually shows movement onto something
• dative after á usually shows location on something

Here the bottle is being moved onto the rock, so Icelandic uses accusative:

• á klettinn = onto the rock

Compare:

• Hún setur flöskuna á klettinn. = She puts the bottle onto the rock.
• Flaskan er á klettinum. = The bottle is on the rock.

English uses on for both ideas, but Icelandic shows the difference with case.

Here svo means then, after that, or next.

It links the two actions in sequence:

1. she puts down the water bottle
2. then she looks for the other hiking shoe

So og leitar svo ... is basically and then looks for ...

Because leita often works with the preposition að when it means look for or search for.

So:

• leita að einhverju = to look for something
• leita að einhverjum = to look for someone

That means the thing being searched for is not a direct object here. It comes after að, and that phrase takes the dative.

Öðrum comes from annar, which means other or second.

Its form changes because Icelandic adjectives/pronouns decline for case, number, and gender. After að, the phrase is in the dative, so annar becomes öðrum.

So:

• annar = other / second
• öðrum = other / second (dative form)

In this sentence it means the other.

Because they are all part of the same noun phrase, and they have to match grammatically.

The phrase after að is in the dative, so everything inside it shows dative:

• öðrum = other (dative)
• gönguskónum = the hiking shoe / shoes (dative)
• sínum = her own (dative)

This kind of agreement is very normal in Icelandic. English does much less of this.

Because sinn is a reflexive possessive. It is used when the possessor is the same as the subject of the clause.

Here the subject is hún (she), and the shoe belongs to that same person, so Icelandic uses sínum.

• hún leitar að gönguskónum sínum = she looks for her own hiking shoe/shoes
• hún leitar að gönguskónum hennar would usually suggest someone else’s hiking shoe/shoes, not her own

So sinn helps avoid ambiguity.

That is the normal Icelandic pattern for possessive pronouns like minn, þinn, sinn.

So Icelandic usually says:

• bókin mín = my book
• skórnir hans = his shoes
• gönguskónum sínum = her own hiking shoe/shoes

To an English speaker, it feels backwards at first, but it is completely standard Icelandic word order.

Formally, it can actually be either.

The form gönguskónum can be:

• dative singular definite = the hiking shoe
• dative plural definite = the hiking shoes

And the surrounding words öðrum and sínum are also forms that can match either singular or plural. So grammar alone does not settle it here; the intended meaning comes from context.

If the meaning shown to the learner is her other hiking shoe, then you should understand it as singular in this sentence.

Because the same subject continues across both verbs.

English does this too:

• She puts the bottle on the rock and then looks for her other shoe.

Icelandic can likewise say:

• Hún setur ... og leitar svo ...

The second hún is simply left out because it is already understood from the first clause.