Þessi spurning er óþörf.

Þessi means this.

It changes form to match the noun’s gender, number, and case. Here it goes with spurning, which is feminine singular nominative, so þessi is the correct form.

A useful detail: þessi is the same form for both masculine and feminine nominative singular, so you identify the gender from the noun, not from þessi alone.

Also, because þessi already means this, Icelandic normally does not add the suffixed definite article to the noun here.

Because spurning is the subject of the sentence, and subjects are normally in the nominative case.

So:

• spurning = nominative singular
• spurningu = accusative/dative singular

In Þessi spurning er óþörf, the question is the thing being described, so nominative is used.

Compare:

• Þessi spurning er óþörf. = This question is unnecessary.
• Ég hef spurningu. = I have a question.

Er means is.

It is the 3rd person singular present tense of vera, the Icelandic verb to be.

So:

• ég er = I am
• þú ert = you are
• hann/hún/það er = he/she/it is

In this sentence, the subject is singular, so er is the correct form.

Óþörf is the feminine singular nominative form of the adjective óþarfur, which means unnecessary or needless.

In Icelandic, adjectives must agree with the noun they describe. Since spurning is feminine singular nominative, the adjective must also be feminine singular nominative:

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

So:

• Þessi stóll er óþarfur. = This chair is unnecessary.
• Þessi spurning er óþörf. = This question is unnecessary.
• Þetta svar er óþarft. = This answer is unnecessary.

Because the sentence uses the verb er (is), and óþörf is a predicate adjective.

So the structure is:

subject + er + adjective

That is the same basic pattern as in English:

• The question is unnecessary.

If you put the adjective directly before the noun, it becomes an attributive adjective instead:

• þessi óþarfa spurning = this unnecessary question

Notice that the form changes there: with þessi before the noun, the adjective takes the weak form óþarfa, not óþörf.

So these are different structures:

• Þessi spurning er óþörf. = This question is unnecessary.
• Þessi óþarfa spurning = this unnecessary question

That vowel change is just part of the adjective’s normal inflection pattern.

The dictionary form is óþarfur, but one of its main forms is:

• óþarfur — masculine
• óþörf — feminine
• óþarft — neuter

So the change from a to ö is not random; it is part of the word’s paradigm. Icelandic has quite a few adjectives and nouns that change their stem vowel in some forms, so it is best to learn these forms together rather than trying to predict everything from English.

Yes, very often.

The prefix ó- is a negative prefix, and it often works like English un-, in-, or non-.

So óþarfur is a negative form meaning something like not necessary / unnecessary.

This is a very useful pattern in Icelandic, but it is still best to learn each word as a real vocabulary item rather than assuming every English un- word will have a direct ó- equivalent.

A rough learner-friendly pronunciation is:

THESS-ih SPURT-ning er OH-thurf

A few important sound notes:

• Þ is like th in think, never like the th in this
• ss is a clear s
• stress usually falls on the first syllable in Icelandic words
• r is typically tapped or trilled, not the English r
• ö does not have an exact English equivalent; you can start with something between the vowel in bird and a short rounded vowel
• the final consonants in óþörf may sound sharper than an English speaker expects

You do not need perfect pronunciation immediately; the most important beginner point is getting þ right and stressing the first syllable.

Not in this sentence.

Þetta is the neuter singular form of this, while spurning is a feminine noun. Since the demonstrative must agree with the noun, you need þessi here.

Compare:

• þessi spurning = this question
• þetta svar = this answer

So the choice depends on the noun’s gender, not on English this, which does not change form.