Eldingin er svo björt að barnið vill fara nær skýlinu.

The ending -in is the suffixed definite article, so eldingin means the lightning.

The base noun is elding = lightning. Icelandic usually adds the to the end of the noun instead of using a separate word. So:

• elding = lightning
• eldingin = the lightning

Here it refers to a specific lightning flash or the lightning being talked about in the situation.

Because adjectives in Icelandic agree with the noun they describe in gender, number, and case.

The noun eldingin is feminine singular nominative, so the adjective must match it. The adjective bjartur = bright has these nominative singular forms:

• masculine: bjartur
• feminine: björt
• neuter: bjart

Since elding is feminine, björt is the correct form.

It means so ... that.

So svo björt að barnið vill fara nær skýlinu means literally:

• svo björt = so bright
• að ... = that ...

This is a very common Icelandic structure for showing result:

• Hann er svo þreyttur að hann sofnar.
  He is so tired that he falls asleep.

Here, að means that.

Icelandic að can have more than one job:

• as a conjunction: that
• as an infinitive marker in some contexts: to

In this sentence, it introduces a subordinate clause, so it means that:

• að barnið vill fara ... = that the child wants to go ...

It is not the infinitive marker here.

The noun barn means child, and barnið means the child.

Again, Icelandic uses a suffixed definite article:

• barn = child
• barnið = the child

Barn is a neuter noun. In this sentence, barnið is the subject of the subordinate clause.

Because after vilja = to want, Icelandic normally uses a bare infinitive, without að.

So:

• vill fara = wants to go

This is similar to English, where we say wants to go, but Icelandic does not always use the infinitive marker in the same places English does. After vilja, just use the infinitive directly.

Skýlinu is dative singular definite.

The base noun is skýli = shelter. In this sentence, it follows nær, and nær takes the dative in this kind of construction.

So:

• skýli = shelter
• skýlinu = the shelter, in dative singular

That gives:

• nær skýlinu = closer to the shelter

Nær means nearer or closer.

In fara nær skýlinu, it expresses movement to a position closer to something:

• fara nær skýlinu = go closer to the shelter

You can think of nær here as behaving a bit like closer to in English. The important thing for learners is that the noun after it goes into the dative.

Because after að, Icelandic is in a subordinate clause, and subordinate clauses do not normally follow main-clause verb-second word order.

So this is normal:

• að barnið vill fara ...

In other words, the subject barnið comes before the finite verb vill.

This is different from many Icelandic main clauses, where verb-second word order is very important.

Yes, but it would not mean exactly the same thing.

• mjög björt = very bright
• svo björt að ... = so bright that ...

The sentence uses svo because it leads naturally into a result clause with að. If you said Eldingin er mjög björt, that would simply mean The lightning is very bright, without the idea of that the child wants to go closer to the shelter as a result.