Önnur skýring er óþörf.

Because önnur has to agree with skýring.

In Icelandic, words like annar/önnur/annað change form for gender, number, and case.

Here, skýring is:

• feminine
• singular
• nominative (the subject of the sentence)

So the correct form is:

• annar = masculine
• önnur = feminine
• annað = neuter

Since skýring is feminine, you say önnur skýring.

It is the feminine form of annar, which usually means other, another, or second, depending on context.

In this sentence, önnur skýring means something like:

• another explanation
• a further explanation

So önnur is functioning like a determiner/adjective that modifies skýring.

Because grammatical gender in Icelandic is a property of the noun itself, not of biological sex.

Skýring is simply a feminine noun, so any adjective or determiner connected to it must use feminine forms.

That is why both parts fit together:

• önnur → feminine
• skýring → feminine noun

This is something learners usually have to memorize along with the noun.

It is in the nominative case.

In the sentence Önnur skýring er óþörf, the phrase önnur skýring is the subject, and subjects are typically in the nominative.

So:

• Önnur skýring = nominative subject
• er = is
• óþörf = predicate adjective describing the subject

Because óþörf must agree with skýring as well.

The adjective óþarfur means unnecessary. Like many Icelandic adjectives, it changes form to match the noun it describes.

Since skýring is:

• feminine
• singular
• nominative

the adjective also appears in the feminine singular nominative form:

• masculine: óþarfur
• feminine: óþörf
• neuter: óþarft

So skýring er óþörf means the explanation is unnecessary / an explanation is unnecessary, with the adjective matching the feminine noun.

This is a normal part of Icelandic adjective inflection. Many adjectives do not just add endings; their stem can also change.

For óþarfur, the feminine form is óþörf. The change from a to ö is part of the adjective’s pattern.

So this is not something special about this sentence only; it is part of how this adjective is declined.

A learner usually just memorizes the main forms together:

• óþarfur (masculine)
• óþörf (feminine)
• óþarft (neuter)

Icelandic does not use an independent indefinite article like English a/an.

So a bare noun like skýring can mean:

• an explanation
• the explanation

depending on context.

In this sentence, önnur skýring naturally means another explanation or a further explanation without needing a separate word for a.

Icelandic usually expresses the with a suffixed article attached to the noun, not with a separate word before it.

For example, the definite form of skýring would be something like skýringin = the explanation.

But here the sentence uses the indefinite idea:

• önnur skýring = another explanation

So there is no definite article.

Er is the present tense of the verb vera = to be.

So here it simply means is.

Structure:

• Önnur skýring = subject
• er = is
• óþörf = unnecessary

So the sentence has the very common Icelandic pattern:

subject + er + adjective

This is a very normal Icelandic sentence.

The order is:

• Önnur skýring = subject
• er = verb
• óþörf = complement/adjective

That is the straightforward neutral order, similar to English:

Another explanation is unnecessary.

Possibly, depending on context, but another explanation or a further explanation is usually the most natural interpretation here.

The word annar and its forms can sometimes mean:

• other
• another
• second

But without extra context, önnur skýring is most naturally understood as another explanation rather than specifically the second explanation.

A rough learner-friendly pronunciation is:

UHN-nur SKEE-ring er OH-thurf

A few notes:

• Ö is a rounded vowel, somewhat like the vowel in French peur or German schön, not like English o.
• skýr- has a long ý, pronounced roughly like ee.
• ð in óþörf is like the th in this, though in connected speech the exact sound can vary.
• The final -f in óþörf is pronounced clearly.

This is only approximate, but it can help as a starting point.

Yes. That would also be grammatical and means roughly the same thing:

• Önnur skýring er óþörf
• Önnur skýring er ekki nauðsynleg

Both mean Another explanation is unnecessary.

The difference is mostly stylistic:

• óþörf is a compact adjective meaning unnecessary
• ekki nauðsynleg literally means not necessary

The original sentence is shorter and more elegant.

This sentence is a good example of three core Icelandic ideas:

1. Adjectives/determiners agree with the noun

   • önnur matches skýring
   • óþörf also matches skýring

2. The subject is in the nominative

   • önnur skýring

3. Icelandic often uses no separate indefinite article

   • no word for a/an

So this is a useful model sentence for building others, such as:

• Ný bók er áhugaverð.
  A new book is interesting.

• Gömul hugmynd er gagnslaus.
  An old idea is useless.

The key pattern is:

[adjective/determiner + noun] + er + [matching adjective]