Greinamerkin í setningunni eru ekki rétt.

Greinamerkin is the definite plural form of greinamerki, a neuter noun meaning punctuation mark.

So the pattern is:

• greinamerki = punctuation mark / punctuation marks
• greinamerkin = the punctuation marks

In English, we often say the punctuation as a collective idea, but Icelandic here uses the plural idea the punctuation marks.

In Icelandic, the definite article is usually attached to the end of the noun instead of being a separate word.

Here are the two examples in the sentence:

• greinamerkin = greinamerki
  • -in = the punctuation marks
• setningunni = setningu/setning
  • definite ending = the sentence in the required case

So instead of a separate word like English the, Icelandic often builds that meaning into the noun itself.

Because the subject is plural.

• er = is (singular)
• eru = are (plural)

The subject here is greinamerkin, meaning the punctuation marks, so the verb must also be plural:

• Greinamerkin ... eru ...

This is normal agreement in Icelandic: the verb agrees with the subject in number.

Because í setningunni belongs to the subject phrase.

The subject is not just greinamerkin by itself. The full subject is:

• Greinamerkin í setningunni = the punctuation marks in the sentence

So the structure is really:

• [Greinamerkin í setningunni] [eru] [ekki rétt]

That means the verb is still in the normal second-position slot in the clause. The prepositional phrase í setningunni is simply modifying the noun greinamerkin.

Because the preposition í takes different cases depending on meaning:

• accusative for motion into
• dative for location in

Here the meaning is location: the punctuation marks are in the sentence, not moving into it. So Icelandic uses the dative.

That is why we get:

• í setningunni = in the sentence

The noun setning is feminine, singular, definite here, and after í with a location meaning it appears in the dative form.

That ending shows two things at once:

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

So setningunni is not a random form you memorize separately from the grammar. It is the form needed because:

1. the sentence is definite
2. í here requires the dative

A useful way to think of it is:

• setning = sentence
• setningunni = in/to/from/etc. the sentence, whenever grammar calls for dative singular definite

Because predicate adjectives in Icelandic agree with the subject in gender and number.

The subject greinamerkin is neuter plural, so the adjective must also be neuter plural:

• réttur = masculine singular
• rétt = neuter singular
• rétt = also neuter plural

So in this sentence, rétt is the correct form for a neuter plural subject.

This can be confusing because the neuter singular and neuter plural forms often look the same.

That is the normal position for ekki in a simple clause.

In Icelandic, ekki usually comes:

• after the finite verb
• and before the word or phrase being negated

So:

• eru ekki rétt = are not correct

This is very natural Icelandic word order.

Yes, that is a very reasonable question. Many neuter nouns in Icelandic have the same form in singular and plural in some cases, especially nominative and accusative.

So greinamerki can look the same whether it means:

• a punctuation mark
• punctuation marks

Context tells you which one is meant.

In this sentence, you know it is plural because of two clues:

• the definite form greinamerkin
• the plural verb eru

So here there is no doubt: it is plural.

It is an adjective, not an adverb.

It describes the subject greinamerkin and means that the punctuation marks are correct / not correct.

This is called a predicate adjective, because it comes after a form of vera (to be):

• Greinamerkin ... eru ekki rétt.

If it were an adverb, it would be modifying the verb, but that is not what is happening here. The sentence is saying something about the punctuation marks themselves.