Örmerkjarnúmerið er í hundaskránni.

Because Icelandic uses compound nouns very heavily. What English often writes as two or more words, Icelandic often writes as one.

So instead of something like microchip number as separate words, Icelandic can package the idea into one noun: Örmerkjarnúmerið.

A very useful rule is:

• the last part of an Icelandic compound is the main noun
• the earlier part tells you what kind of thing it is

Here, the important grammatical core is númer (number). The earlier material specifies what kind of number.

Also, compounds often contain linking sounds or forms in the middle, so you cannot always split them up in a perfectly English-looking way. Learners usually do best by noticing the final core noun and then learning the whole compound as a unit.

In Icelandic, the last element usually determines the gender of the whole compound.

• númer is neuter, so örmerkjarnúmer is neuter
• skrá is feminine, so hundaskrá is feminine

That matters because Icelandic endings change for:

• gender
• number
• case
• definiteness

So even though these are long compounds, grammatically they behave like their final element.

Because Icelandic usually expresses the as an ending attached to the noun, not as a separate word.

In this sentence:

• númerið = the number
• skránni = the registry / the register in a particular case form

So:

• -ið is part of the definite form of a neuter singular noun
• -nni is part of the definite feminine dative singular form here

This is one of the biggest differences from English: Icelandic often builds the into the noun itself.

Because the preposition í changes case depending on meaning:

• í + dative = location, in
• í + accusative = movement, into

Here the sentence describes where the number is located, so Icelandic uses dative:

• í hundaskránni = in the dog registry

If the sentence were about putting something into the registry, you would expect accusative instead.

This location-vs-movement contrast is very common in Icelandic.

That is a normal feature of Icelandic compounds. The first noun often appears in a linking form, frequently related to a genitive form.

So hundaskrá is built from:

• hundur = dog
• skrá = register, list, registry

The hunda- part is the form used in the compound. You do not need to translate it literally every time; it is best to learn hundaskrá as the standard compound meaning dog registry.

This kind of pattern is extremely common in Icelandic vocabulary.

Prepositions do not match English one-for-one.

English might talk about something being on a register or in a registry, depending on context. Icelandic has its own habits, and with a registry, list, or database-like idea, í is very natural for saying something is in it.

So a good habit is to learn nouns together with their usual prepositions, rather than assuming Icelandic will choose the same preposition English does.

It is nominative singular definite.

Why?

• it is the subject of the sentence
• subjects are normally in the nominative
• the head noun is númer, which is neuter
• the definite nominative singular form is númerið

So the whole compound appears as Örmerkjarnúmerið.

Because this sentence follows a very normal Icelandic main-clause pattern:

• Örmerkjarnúmerið = first element
• er = finite verb in second position
• í hundaskránni = rest of the clause

Icelandic is often described as a verb-second language in main clauses. In this sentence, the subject happens to come first, so the result looks quite English-like.

You can see the rule more clearly if another element is moved to the front:

• Í hundaskránni er örmerkjarnúmerið.

The verb er still stays in second position.

A rough learner-friendly approximation is:

UR-merk-yar-NOO-mer-ith er ee HUN-da-skrowt-nih

A few helpful points:

• ö is roughly like German ö, or somewhat like the vowel in British burn
• j sounds like y
• ú sounds like oo
• í sounds like ee
• á sounds like ow in now
• ð is the soft th sound in this
• Icelandic nn before certain endings can sound different from what English speakers expect, so skránni is not pronounced like simple English skranni

Also, Icelandic stress normally falls on the first syllable of each word.