Eyrnalokkarnir hennar passa vel við kjólinn.

It is a compound plus a definite ending:

• eyrna- = of ears (from eyra, ear)
• lokkar = rings / dangling pieces, used in the word for earrings
• -nir = the for a masculine plural noun

So eyrnalokkarnir means the earrings.

This is very normal in Icelandic: words are often built as compounds, and the definite article is usually added to the end of the noun instead of written as a separate word.

Because it is a masculine plural noun in the nominative definite.

The base noun is eyrnalokkar = earrings.
When you make it definite, you add the article ending:

• eyrnalokkar = earrings
• eyrnalokkarnir = the earrings

The ending -nir is a common nominative plural definite ending for masculine nouns.

In Icelandic, possessive words like hennar often come after the noun:

• eyrnalokkarnir hennar = her earrings

This is very natural Icelandic word order. English usually puts the possessive first, but Icelandic often places it after the noun, especially with pronoun possessors like hennar, hans, and þeirra.

Hennar means her.

More specifically, it is the genitive form of hún = she. Icelandic often uses these genitive pronoun forms to show possession:

• hans = his
• hennar = her
• þeirra = their

So eyrnalokkarnir hennar literally means the earrings of her, but in natural English that is just her earrings.

Because the subject is plural: eyrnalokkarnir = the earrings.

In Icelandic, verbs agree with the subject in number:

• Kjóllinn passar = the dress fits / matches
• Eyrnalokkarnir passa = the earrings fit / match

So passa is the correct present tense form for a plural subject.

As a whole, passa vel við means go well with, match well with, or suit.

So the sentence means that the earrings match the dress well.

This is important because passa can have different meanings depending on context. It can mean things like:

• fit
• suit
• match
• sometimes even be careful / watch out in other expressions

But here, with við, it means match / go with.

Við is the preposition used with passa when talking about one thing matching another.

So:

• passa við eitthvað = to match something / go with something

In this sentence:

• Eyrnalokkarnir passa vel við kjólinn
  = The earrings go well with the dress.

You can think of við here as part of the expression passa við.

Because við here takes the accusative case, and kjóllinn changes in the accusative.

The noun is:

• nominative: kjóllinn = the dress
• accusative: kjólinn = the dress

So after við in this meaning, Icelandic uses the accusative:

• við kjólinn

This is one of the big things English speakers have to get used to: the noun changes form depending on its role and the preposition used with it.

The ending -inn is the definite article attached to the noun.

• kjóll = dress
• kjóllinn / kjólinn = the dress

In this sentence the accusative form is used, so you see kjólinn.

Icelandic usually adds the directly onto the noun instead of using a separate word.

Yes. Passa can mean fit in the sense of size, but in this sentence it means match / go well with.

For example:

• Kjóllinn passar mér.
  = The dress fits me.

But:

• Eyrnalokkarnir passa vel við kjólinn.
  = The earrings match the dress well.

So the meaning depends on the pattern around the verb.

The basic structure is:

• Eyrnalokkarnir hennar = subject
• passa = verb
• vel = adverb
• við kjólinn = prepositional phrase

So literally:

• Her earrings
  • match
    • well
      • with the dress

That is a very normal Icelandic sentence pattern.

Vel means well, and its placement here is natural Icelandic word order.

• passa vel við = match well with

This is similar to English, where well often comes after the verb:

• They match well with the dress.

So this part is not especially strange for English speakers.

A rough pronunciation guide for an English speaker is:

• Eyrnalokkarnir ≈ AYRT-na-lok-kar-nir
• hennar ≈ HEN-nar
• passa ≈ PAH-sa
• vel ≈ veh-l
• við ≈ vith or vithh
• kjólinn ≈ KYOH-lin

A few helpful points:

• ey is usually like ay
• ll in modern Icelandic often has a special pronunciation, but in a rough learner-friendly version you can think of kjólinn as close to kyoh-lin
• ð is like the th in this, though at the end of a word it can be weaker

Yes, but the meaning would change slightly.

• Eyrnalokkarnir hennar passa vel við kjólinn.
  = Her earrings go well with the dress.

Without the definite endings:

• Eyrnalokkar hennar passa vel við kjól.
  = Her earrings go well with a dress / dresses
  depending on context

The definite endings make the sentence sound more specific: a particular pair of earrings and a particular dress.

Yes, three very useful things:

1. The definite article is added to the noun

   • eyrnalokkar → eyrnalokkarnir
   • kjóll → kjólinn

2. Possessive pronouns often come after the noun

   • eyrnalokkarnir hennar = her earrings

3. Learn the expression passa við as a chunk

   • passa við = match / go with

If you remember those three patterns, this sentence becomes much easier to understand and reuse.