Músin er á borðinu við tölvuna.

Because Icelandic usually expresses the by attaching it to the end of the noun.

• mús = mouse
• músin = the mouse

So Músin means the mouse. In this sentence it is the subject, so it appears in the nominative singular definite form.

Because Icelandic does not have one single unchanging word like English the. The definite article changes depending on:

• gender
• number
• case

So here you get different forms:

• músin = feminine, nominative singular, definite
• borðinu = neuter, dative singular, definite
• tölvuna = feminine, accusative singular, definite

All three mean the ..., but the endings are different because the grammar is different.

Because á can take different cases depending on meaning.

In this sentence, the mouse is already located on the table, so á takes the dative:

• á borðinu = on the table

If there were motion onto the table, Icelandic would usually use the accusative instead:

• á borðið = onto the table

So the dative here tells you this is a location, not a movement.

Because the preposition við takes the accusative.

So:

• tölva = computer
• tölvuna = the computer in the accusative singular

Here við tölvuna means by the computer / next to the computer.

No. In this sentence, við means by, beside, or next to.

That can confuse English speakers, because with is usually með in Icelandic.

So:

• við tölvuna = by the computer
• með tölvunni would mean something more like with the computer

It is nominative singular.

That is because músin is the subject of the sentence — the thing that is somewhere.

In a basic sentence with að vera (to be), the subject is normally in the nominative:

• Músin er ... = The mouse is ...

It can mean either, just like English mouse.

So this sentence could mean:

• the animal mouse is on the table by the computer, or
• the computer mouse is on the table by the computer

Usually the context tells you which one is meant. If you want to be completely clear, Icelandic also has tölvumús for computer mouse.

er is the 3rd person singular present of að vera = to be.

Since músin is singular, the verb is singular too:

• músin er = the mouse is

So this is just the normal present-tense form for it is / the mouse is.

No — this is a very normal, neutral Icelandic sentence.

It follows a basic pattern:

• Músin = subject
• er = verb
• á borðinu við tölvuna = location phrase

So it is essentially:

• The mouse is on the table by the computer

Icelandic word order can be more flexible than English, but this version is the most straightforward one.

The basic forms are:

• mús = mouse
• borð = table
• tölva = computer

These are the forms you would usually look up in a dictionary. In the sentence, they change form because Icelandic nouns inflect for:

• case
• definiteness
• gender