Nóttin virðist eilíf.

Nóttin means the night. The ending -in is the definite article attached to the noun.

So:

• nótt = night
• nóttin = the night

This is very common in Icelandic: instead of using a separate word like English the, Icelandic often adds the article to the end of the noun.

The dictionary form is nótt.

That is the indefinite singular nominative form, which is the form you usually look up in a dictionary.
In the sentence, it appears as nóttin because it is:

• singular
• nominative
• definite (the night)

It is in the nominative because it is the subject of the sentence.

In Nóttin virðist eilíf, the thing that seems something is the night, so nóttin is the subject. Subjects are normally in the nominative in Icelandic.

Virðist comes from the verb virðast, which means to seem.

Here, virðist is the 3rd person singular present tense form, used with a singular subject like nóttin.

So:

• ég virðist would not be correct
• hún virðist = she seems
• nóttin virðist = the night seems

A useful thing to remember is that virðast is often followed by an adjective describing how something seems.

The adjective has to agree with the noun it describes.

Here, eilíf matches nóttin, which is:

• feminine
• singular
• nominative

So the adjective also appears in the feminine singular nominative form: eilíf.

This kind of agreement is very important in Icelandic. Adjectives change form depending on:

• gender
• number
• case
• sometimes definiteness/declension pattern

Because the sentence uses virðist = seems, not er = is.

English says The night seems eternal, and Icelandic does the same structure:

• Nóttin = the night
• virðist = seems
• eilíf = eternal

So there is no need for a separate is. The verb virðist already functions as the main verb of the sentence.

It is acting like a predicate adjective.

That means it is not sitting directly before the noun like the eternal night. Instead, it comes after the verb and describes the subject through the verb:

• Nóttin er eilíf = The night is eternal
• Nóttin virðist eilíf = The night seems eternal

So eilíf is linked to nóttin through virðist.

Yes, but the basic neutral order here is:

• Subject + Verb + Adjective
• Nóttin virðist eilíf

Icelandic does allow other word orders in some contexts, especially for emphasis or in subordinate clauses, but this is the most straightforward and natural order for a simple statement.

Because Icelandic is a case language, word order can sometimes be more flexible than in English, but that does not mean every rearrangement sounds equally natural.

It would be:

• Næturnar virðast eilífar. = The nights seem eternal.

Changes:

• nóttin → næturnar (the nights)
• virðist → virðast because the subject is now plural
• eilíf → eilífar to agree with a feminine plural nominative noun

This is a good example of how both the verb and adjective can change when the subject changes.

A learner may notice that Icelandic spelling and pronunciation do not always match English expectations.

In nóttin:

• ó is a long vowel, roughly like o in English go, though not exactly the same
• tt in Icelandic is often pronounced with pre-aspiration, something like a brief h sound before the t
• the ending -in is the attached definite article

So nóttin does not sound exactly how an English speaker might guess from the spelling. The tt is one of the parts learners usually need to hear from native audio to get right.

Yes, but it changes the feel of the sentence.

• Nóttin virðist eilíf = The night seems eternal
• Nótt virðist eilíf = Night seems eternal or A night seems eternal, depending on context

Without the article, it sounds more general, poetic, or less specifically tied to one particular night.
With -in, it clearly refers to the night, a definite one.

Yes. The dictionary form is usually the masculine singular nominative form:

• eilífur = dictionary form
• eilíf = feminine singular nominative
• eilíft = neuter singular nominative/accusative

So in this sentence you see eilíf because it agrees with the feminine noun nóttin, but if you looked the adjective up, you would usually find it under eilífur.