Barnabæturnar minnka.

Because Icelandic usually puts the definite article on the end of the noun instead of using a separate word.

• barnabætur = child benefits
• barnabæturnar = the child benefits

Here, -nar is the definite ending for this noun form.

It has three parts:

• barna- = related to children
• bætur = benefits, compensation
• -nar = the

So the whole word is a compound noun with the definite article added to the end.

Because the first part of this compound comes from barna, the genitive plural form of barn.

This is very common in Icelandic compounds. A form meaning roughly of children is used to build the compound, even though in natural English we usually translate it more simply as child-.

So:

• barn = child
• barna = of children
• barnabætur = literally something like children’s benefits, but understood as child benefits

Because this word is normally used as a plural noun in Icelandic, much like English benefits.

Even if English might sometimes use a singular expression like child benefit or family allowance, Icelandic commonly uses the plural barnabætur. Because of that, the verb also appears in the plural.

It is nominative plural.

The reason is simple: it is the subject of the sentence, and subjects are typically in the nominative case in Icelandic.

So in Barnabæturnar minnka, the thing doing the decreasing is barnabæturnar, which makes it nominative.

It is feminine.

The main part of the compound is bætur, which comes from bót, a feminine noun. In Icelandic compounds, the grammatical gender normally comes from the final element of the compound, so barnabætur is feminine as well.

That matters for endings like the definite article and for words that agree with the noun.

Because the subject is plural.

The verb minnka agrees with a third-person plural subject:

• hann/hún minnkar = he/she decreases or is decreasing
• þeir/þær/þau minnka = they decrease or are decreasing

Since barnabæturnar is plural, the sentence uses minnka.

Here it is a present-tense finite verb, specifically third person plural.

This can be confusing because minnka is also the dictionary form of the verb:

• að minnka = to decrease
• þær minnka = they decrease / are decreasing

So the form looks the same, but the sentence structure tells you which one it is. In Barnabæturnar minnka, it is clearly the main verb of the sentence.

It can cover both ideas.

Icelandic present tense often corresponds to both:

• English simple present: decrease
• English present progressive: are decreasing

So this sentence can naturally be understood as either a general present statement or an ongoing change, depending on context.

Yes.

That version is also natural and puts more focus on the idea that the decrease is happening right now or is in progress.

Very roughly:

• Barnabæturnar minnka = The child benefits decrease / are decreasing
• Barnabæturnar eru að minnka = The child benefits are decreasing

The simple present is already very common in Icelandic, so the shorter sentence is perfectly normal.

You would usually look up:

• barnabætur for the noun
• að minnka for the verb

Why not barnabæturnar? Because the -nar part is just the definite ending, not the basic dictionary form.