Frádrátturinn og barnabæturnar eru rétt.

In Icelandic, the is usually not a separate word. It is most often added to the end of the noun as a suffix.

So here:

• frádrátturinn = frádráttur
  • definite article
• barnabæturnar = barnabætur
  • definite article

That is why you do not see a separate word like English the.

The dictionary form is frádráttur.

This is a masculine singular noun, and in the nominative definite singular it becomes frádrátturinn.

A useful way to think about it is:

• frádráttur = deduction
• frádrátturinn = the deduction

With many masculine nouns ending in -ur, the definite nominative singular form looks like -urinn.

The base form is barnabætur.

This word is:

• plural
• feminine
• a compound noun

Then the definite article is added:

• barnabætur = child benefits
• barnabæturnar = the child benefits

So -nar here is the definite ending for this plural feminine form.

Because the noun itself is normally used as a plural word when referring to child benefits as a benefit/payment category.

So Icelandic treats it as plural in the same way English says benefits, not benefit, in this meaning.

That is why the sentence has:

• barnabæturnar
• and the plural verb eru

Barna- is the first part of the compound and comes from börn / barn in a genitive-plural compound form.

So the compound literally has the sense of something like:

• benefits for children
• or children’s benefits

This is very common in Icelandic: the first part of a compound often appears in a genitive or linking form.

Because the subject is not just one thing. It is:

• Frádrátturinn
• og barnabæturnar

When two subjects are joined by og (and), the subject is plural overall, so the verb must also be plural.

So:

• er = is
• eru = are

That is why the sentence uses eru.

This is a very common learner question.

Rétt is an adjective here, and it agrees with the subject. But the subject is a combination of:

• one masculine singular noun: frádrátturinn
• one feminine plural noun: barnabæturnar

When Icelandic has a mixed-gender coordinated subject like this, it often uses the neuter plural as the default agreement form for the predicate adjective.

The adjective réttur has these relevant forms:

• réttur = masculine singular
• rétt = feminine singular / neuter singular
• réttar = feminine plural
• rétt = neuter plural

So the rétt in this sentence is best understood as neuter plural agreement.

That is why you get:

• Frádrátturinn og barnabæturnar eru rétt.

Compare:

• Frádrátturinn er réttur.
• Barnabæturnar eru réttar.

But together, the mixed subject gives rétt.

Here it is an adjective, not an adverb.

It comes after eru and describes the subject:

• Frádrátturinn og barnabæturnar eru rétt.

So it means the deduction and the child benefits are correct/right.

As an adverb, rétt can also mean something like correctly in other sentences, but that is not what is happening here.

They are in the nominative, because they are the subject of the sentence.

So:

• frádrátturinn = nominative singular definite
• barnabæturnar = nominative plural definite

This matches their role as the things that are correct.

Yes. This is a very straightforward Icelandic sentence:

• subject: Frádrátturinn og barnabæturnar
• verb: eru
• predicate adjective: rétt

So the structure is basically:

• The deduction and the child benefits are correct.

There is nothing unusual about the word order here; the main interesting parts are the definite endings and the agreement in eru and rétt.