Armbandið hennar passar vel við hálsmenið.

Because both nouns are neuter singular definite.

In Icelandic, the definite article is usually attached to the end of the noun instead of being a separate word like the in English.

• armband = bracelet

• armbandið = the bracelet

• hálsmen = necklace
• hálsmenið = the necklace

The ending -ið is the usual definite ending for many neuter nouns in the singular.

Hennar means her.

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

• armbandið hennar = her bracelet
• literally: the bracelet her

That word order is very normal in Icelandic, even though it feels reversed compared with English.

Because Icelandic commonly puts this kind of possessive after the noun.

So the most natural pattern is often:

• noun + possessive
• bíllinn hans = his car
• taskan hennar = her bag

A fronted possessive like hennar armband is much less common and would usually need a special context or emphasis. For a learner, armbandið hennar is the normal pattern to remember.

As a phrase, passa vel við means something like:

• go well with
• match well with
• suit

So this is not about physical size or whether something literally fits onto something else. Here it means the bracelet and the necklace look good together in style, color, or design.

Passar is the 3rd person singular present tense of the verb passa.

Here it agrees with the subject armbandið hennar:

• armbandið hennar passar = her bracelet matches / goes well

Some useful related forms are:

• að passa = to fit / suit / match
• ég passa = I fit / match
• það passar = it fits / it works / it matches

The verb passa can have several meanings depending on context, so the phrase around it matters a lot.

Vel is an adverb meaning well.

It modifies passar:

• passar = matches / goes with
• passar vel = matches well / goes well with

So vel adds the idea that the match is a good one.

In this sentence, við means with in the sense of in relation to or together with.

After passa, Icelandic often uses við to show what something matches:

• passa við eitthvað = to match something
• passa vel við eitthvað = to go well with something

So:

• Armbandið hennar passar vel við hálsmenið.
• Her bracelet goes well with the necklace.

Here við takes the accusative.

So hálsmenið is accusative singular definite. However, with many neuter nouns, the nominative and accusative forms are the same, so it still looks like hálsmenið.

That means:

• nominative definite: hálsmenið
• accusative definite: hálsmenið

So the case changes grammatically, but not visibly in this noun form.

Yes. Even though an English speaker might first think of armband as something worn around the upper arm, in Icelandic armband commonly means bracelet.

So:

• armband = bracelet
• hálsmen = necklace

This is a good example of a word that looks familiar to English but is used a bit differently.

The sentence follows a normal Icelandic main-clause pattern:

• Armbandið hennar = subject
• passar = verb
• vel við hálsmenið = rest of the predicate

So the structure is basically:

• Subject + Verb + Adverb + Prepositional phrase

That is quite similar to English here, which makes this sentence easier than many other Icelandic sentences.

Yes. You could rearrange it depending on what you want to emphasize.

For example:

• Hálsmenið passar vel við armbandið hennar.

That means essentially the same thing, but now the necklace is the grammatical subject and gets more attention.

In the original sentence, the focus starts with her bracelet.

Because Icelandic usually does not use a separate definite article like English the. Instead, definiteness is built into the noun itself with an ending.

So instead of:

• the bracelet
• the necklace

Icelandic says:

• armbandið
• hálsmenið

This is one of the most important structural differences between English and Icelandic.