Eftir hádegismat tekur hún stuttan hádegislúr í rimlarúminu.

Because Icelandic is a verb-second language. That means the finite verb usually stays in the second slot of a main clause.

So when the sentence begins with the time phrase Eftir hádegismat, the verb tekur comes next, and the subject hún follows it:

Eftir hádegismat | tekur | hún ...

If the subject came first, then you would get the more basic order:

Hún tekur stuttan hádegislúr í rimlarúminu eftir hádegismat.

Both are grammatical, but the original sentence puts extra focus on when it happens.

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

Here, hádegislúr is:

• masculine
• singular
• direct object of tekur

That means the adjective must be masculine accusative singular, which is stuttan.

So:

• stuttur hádegislúr = a short midday nap as a subject
• stuttan hádegislúr = a short midday nap as an object

English does not change short, but Icelandic does.

Yes, very much. Icelandic often uses taka with nouns in expressions like this, just as English says take a nap, take a walk, and so on.

So taka hádegislúr means to take a midday nap or simply to nap.

You could also hear similar expressions such as:

• taka lúr = take a nap
• fá sér lúr = have a nap

So this is a normal, idiomatic way to say it.

Good question. Sér is not required here.

Both of these are natural:

• hún tekur lúr
• hún tekur sér lúr

The version with sér can sound a little more like she has herself a nap, but in everyday usage both patterns are common and understandable. The sentence without sér is perfectly fine.

That -s- is very common in Icelandic compounds. The first part of a compound often appears in a linking form, frequently related to the genitive.

So:

• hádegi = noon, midday
• hádegis- = linking form used in compounds

That gives:

• hádegismatur = lunch
• hádegislúr = midday nap

This is something you will see a lot in Icelandic compounds, so it is worth getting used to.

Because meal words are often used without a definite article when speaking generally, much like in English.

So:

• eftir hádegismat = after lunch

This is a general time expression, not necessarily after the specific lunch. If you wanted to refer to a particular lunch already known in the conversation, you could use a definite form such as hádegismatinn.

The ending -inu shows two things at once:

• the noun is definite: the crib
• the noun is in the dative singular

Icelandic usually puts the definite article onto the end of the noun instead of using a separate word like English the.

So:

• rimlarúm = crib, cot
• rimlarúmið = the crib
• rimlarúminu = in the crib / in the cot, with the case required here

This kind of attached article is a basic feature of Icelandic grammar.

Yes. Í can take two different cases, depending on meaning:

• accusative for motion into
• dative for location in

Here the meaning is location: she is taking the nap in the crib, not moving into it. So Icelandic uses the dative:

í rimlarúminu

Compare:

• Hún sefur í rimlarúminu. = She sleeps in the crib.
• Hún fer í rimlarúmið. = She goes into the crib/bed.

That location-vs-motion contrast is very important with Icelandic prepositions.

Rimlarúm is a compound noun meaning a crib or cot.

Literally, it is something like:

• rimlar = bars / slats
• rúm = bed

So the idea is a slatted bed or barred bed, which is why the natural English meaning is crib or cot.

This is a very Icelandic way of building vocabulary: instead of a completely separate word, the language often combines familiar elements into a compound.

This is a good example of why Icelandic cases can be tricky for learners: the form hádegismat does not clearly show the case by itself.

For the noun hádegismatur, the singular oblique forms can look the same, so the ending does not tell you everything on its own. That means you often have to learn:

• the noun’s declension
• the preposition’s case behavior
• the whole phrase together

So in practice, many learners simply memorize eftir hádegismat as a set expression meaning after lunch.

Yes. You could say:

Hún tekur stuttan hádegislúr í rimlarúminu eftir hádegismat.

That is grammatical. The difference is mainly information structure and emphasis.

• Eftir hádegismat tekur hún ... puts the time frame first and triggers verb-second order.
• Hún tekur ... eftir hádegismat starts more neutrally with the subject.

So the original sentence is not the only possible word order, but it is a very natural one.