Leigutekjurnar eru réttar.

Icelandic makes heavy use of compound nouns. Leigutekjurnar is built from leigu- + tekjur + the definite article -nar.

• leigu- = rental, rent-related
• tekjur = income, revenues, earnings
• -nar = the for a feminine plural noun

So instead of using several separate words, Icelandic often combines them into one.

Because tekjur is normally used as a plural noun in Icelandic when talking about income or revenues. English often uses income as a singular mass noun, but Icelandic commonly uses the plural idea of earnings/revenues.

So even if the English meaning looks singular, the Icelandic grammar here is plural.

Because the subject is plural.

The verb vera = to be changes according to number:

• er = is, for singular
• eru = are, for plural

Since leigutekjurnar is plural, Icelandic uses eru.

Because adjectives in Icelandic must agree with the noun they describe in gender, number, and case.

Here, leigutekjurnar is:

• feminine
• plural
• nominative

So the adjective réttur appears in the matching form réttar.

This is the feminine plural nominative form.

The dictionary form of an adjective is usually the masculine singular nominative, which is why you often learn réttur first.

But in real sentences, Icelandic adjectives change form. Here the noun is feminine plural, so réttur has to change to réttar.

You can think of it like this:

• réttur = base form you learn in the dictionary
• réttar = the form required by this particular noun

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

In a sentence like this:

• Leigutekjurnar = the subject
• eru = the verb
• réttar = predicate adjective

Also, after vera (to be), the adjective is normally nominative too, so réttar matches the subject in nominative plural feminine.

-nar is the suffixed definite article for a feminine plural noun in this form.

So:

• leigutekjur = rental income / rental revenues
• leigutekjurnar = the rental income / the rental revenues

Unlike English, Icelandic usually adds the to the end of the noun instead of putting it in front as a separate word.

It is an adjective.

It describes the subject leigutekjurnar, even though it comes after the verb eru. This is called a predicate adjective.

So the structure is:

• The rental income/revenues
• are
• correct

The adjective is not modifying the verb; it is describing the subject.

Not always. The adjective réttur can have several related meanings, such as right, correct, proper, or just, depending on context.

In this sentence, with eru, it means correct or right in the sense of being accurate.

It would be:

Leigutekjur eru réttar.

That is the indefinite version, without the suffixed article -nar.

So the difference is:

• Leigutekjur eru réttar. = Rental income / rental revenues are correct.
• Leigutekjurnar eru réttar. = The rental income / the rental revenues are correct.

Yes. This is very common and is something English speakers have to get used to.

Icelandic often expresses financial ideas with plural nouns such as tekjur. So even if the natural English translation is income, the Icelandic grammar may still be plural:

• plural noun
• plural verb
• plural adjective

That is exactly what happens in Leigutekjurnar eru réttar.